<PAGE>

                                                                   EXHIBIT 10.22


                   MILLENNIUM CENTER - NORTH AND EAST TOWERS

                                 OFFICE LEASE


                                BY AND BETWEEN


                             114 MILLENNIUM, LTD.


                                 AS LANDLORD,


                                      AND


                           DATA RETURN CORPORATION,

                                   AS TENANT



NOTICE:   THIS LEASE CONTAINS A YEAR 2000 READINESS DISCLOSURE STATEMENT.
<PAGE>

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                            PAGE
                                                                            ----
<S>                                                                         <C>
1.   Definitions and Basic Lease Provisions....................................1
     --------------------------------------
2.   Leased Premises...........................................................3
     ---------------
3.   Lease Term................................................................3
     ----------
4.   Acceptance of Leased Premises.............................................3
     -----------------------------
5.   Rent Payments.............................................................4
     -------------
6.   Electricity...............................................................5
     -----------
7.   Services by Landlord......................................................7
     --------------------
8.   Service Interruptions; Alternative Providers..............................9
     --------------------------------------------
9.   Operating Costs..........................................................10
     ---------------
10.  Security Deposit.........................................................15
     ----------------
11.  Assignment and Subletting................................................15
     -------------------------
12.  Repair and Maintenance...................................................19
     ----------------------
13.  Alterations and Additions by Tenant......................................19
     -----------------------------------
14.  Use and Occupancy........................................................21
     -----------------
15.  Mechanics' Liens - Tenant's Obligations..................................22
     ---------------------------------------
16.  Limitations on Liability of Landlord Parties; Waiver.....................23
     ----------------------------------------------------
17.  Indemnification..........................................................24
     ---------------
18.  Tenant's Insurance.......................................................25
     ------------------
19.  Landlord's Insurance.....................................................26
     --------------------
20.  Rights Reserved by Landlord..............................................26
     ---------------------------
21.  Fire or Other Casualty...................................................28
     ----------------------
22.  Condemnation.............................................................30
     ------------
23.  Taxes on Tenant's Property...............................................31
     --------------------------
24.  Waiver of Subrogation....................................................31
     ---------------------
25.  Surrender Upon Termination or Expiration; Holdover.......................31
     --------------------------------------------------
26.  Removal of Tenant's Property.............................................32
     ----------------------------
27.  Events of Default........................................................33
     -----------------
28.  Landlord's Remedies......................................................34
     -------------------
29.  No Implied Waiver........................................................36
     -----------------
30.  Waiver by Tenant.........................................................36
     ----------------
31.  Legal Expenses...........................................................37
     --------------
32.  Subordination............................................................37
     -------------
33.  Quiet Enjoyment..........................................................37
     ---------------
34.  Notice of Landlord's Default.............................................37
     ----------------------------
35.  Project Rules and Regulations............................................38
     -----------------------------
36.  Estoppel Certificate.....................................................38
     --------------------
37.  Notices..................................................................38
     -------
38.  Hazardous Materials......................................................39
     -------------------
39.  Business Purpose.........................................................40
     ----------------
40.  Severability.............................................................40
     ------------
41.  No Merger................................................................41
     ---------
42.  Force Majeure............................................................41
     -------------
43.  Brokerage; Mutual Indemnities............................................41
     -----------------------------
44.  Gender...................................................................41
     ------
45.  Joint and Several Liability..............................................42
     ---------------------------
46.  No Representations.......................................................42
     ------------------
</TABLE>

                                       i
<PAGE>

<TABLE>
<S>                                                                          <C>
47.  Entire Agreement; Amendments............................................42
     ----------------------------
48.  Paragraph Headings......................................................42
     ------------------
49.  Binding Effect..........................................................42
     --------------
50.  Exhibits................................................................42
     --------
51.  Counterparts............................................................42
     ------------
52.  Rental Tax..............................................................43
     ----------
53.  Parking.................................................................43
     -------
54.  Tenant's Service Providers..............................................45
     --------------------------
55.  Option to Expand the Leased Premises....................................45
     ------------------------------------
56.  Option to Extend Lease Term for the Original Leased Premises............46
     ------------------------------------------------------------
57.  Security Disclaimer.....................................................48
     -------------------
58.  Landlord's Consent and Approvals........................................48
     --------------------------------
59.  Intentionally Deleted...................................................48
     ---------------------
60.  Right of First Notice...................................................48
     ---------------------
61.  Limitation of Actions...................................................49
     ---------------------
62.  Year 2000 Readiness Disclosure Statement................................49
     ----------------------------------------
63.  Time: Exercise of Options...............................................50
     -------------------------
64.  Execution and Approval of Lease.........................................50
     -------------------------------
</TABLE>


LIST OF EXHIBITS

EXHIBIT A:  Floor Plan of the Leased Premises
EXHIBIT B:  The Land
EXHIBIT C:  Project Rules and Regulations
EXHIBIT D:  Contractor Insurance Requirements
EXHIBIT E:  Estoppel Certificate
EXHIBIT F:  Tenant Finish Construction
EXHIBIT G:  Floor Plan of Suite 450E
EXHIBIT H:  Floor Plan of the First Notice Space
EXHIBIT I:  List of Permitted Temporary Occupants
EXHIBIT J:  Minimum Rent Schedule
EXHIBIT K:  Subordination, Nondisturbance, and Attornment Agreement

                                      ii
<PAGE>

                                 OFFICE LEASE

This Office Lease (this Lease) is entered into as of November 15, 1999 (the date
of this Lease), by 114 MILLENNIUM, LTD., a Texas limited partnership (Landlord),
and, DATA RETURN CORPORATION, a Texas corporation (Tenant).

1.   Definitions and Basic Lease Provisions.
     --------------------------------------

     Some of the basic provisions and defined terms of this Lease are as
     follows:

     Project:                 Millennium Center, Irving, Texas, including the
                              North and East Towers, associated parking garages,
                              the Land described on Exhibit B, and other
                                                    ---------
                              improvements erected upon the Land from time to
                              time.

     Buildings:               The North Tower and the East Tower of the Project,
                              222 West Las Colinas Boulevard, Irving, Texas
                              75039.

     Leased Premises:         Approximately 68,765 Rentable Square Feet (defined
                              in Paragraph 2(b)), as shown on Exhibit A,
                                                              ---------
                              consisting of Suite 250E (approximately 6,428 RSF)
                              on Floor 2 of the East Tower, Suite 260E
                              (approximately 5,009 RSF) on Floor 2 of the East
                              Tower, Suite 300N (approximately 13,666 RSF) on
                              Floor 3 of the North Tower, Suite 350E
                              (approximately 22,514 RSF) on Floor 3 of the East
                              Tower, and Suite 400N (approximately 21,148 RSF)
                              on Floor 4 of the North Tower. (See Exhibit J)
                                                                 ---------

     Total Project Area:      835,044 Rentable Square Feet.

     Minimum Rent:            See Exhibit J attached to this Lease.
                                  ---------

     Rent:                    The Minimum Rent and all other amounts payable by
                              Tenant to Landlord under this Lease.

     Commencement Date:       The date of this Lease.

     Suites 300N & 350E
     Commencement Date:       April 1, 2000 - Suites 300N & 350E. (See Paragraph
                              C of Exhibit F)
                                   ---------

     Suite 400N Commencement
     Date:                    June 1, 2000 - Suite 400N. (See Paragraph C of
                              Exhibit F)
                              ---------

     Suite 450E Commencement
     Date:                    November 1, 2001 - Suite 450E. (See Paragraph 55)

                                                                          Page 1
<PAGE>

     Expiration Date:           May 31, 2003. (See Paragraph 3 and Paragraph C
                                of Exhibit F)
                                   ---------

     Lease Term:                Approximately 42.5 months, commencing on the
                                Commencement Date and ending on the Expiration
                                Date.

     Base Year for Operating
     Costs:                     Calendar year 2000.

     Tenant's Broker            Baker Commercial Realty, Inc., a Texas
                                corporation.

     Landlord's Broker          Cousins Stone LP, a Texas limited partnership.

     Security Deposit:          $134,664.79.  (See Paragraph 55(d))

     Parking:                   See Paragraph 53.

     Permitted Use:             General business offices.

     Tenant Party(ies):         Tenant, the Permitted Temporary Occupants
                                (defined in Paragraph 11(a)) and their
                                respective officers, directors, shareholders,
                                partners, trustees, members, agents,
                                contractors, subcontractors, employees,
                                licensees, invitees, and all persons and
                                entities claiming through any of these persons
                                or entities.

     Landlord Party(ies):       Landlord and its authorized representatives and
                                their respective officers, directors,
                                shareholders, partners, trustees, members,
                                agents, employees, property manager (including
                                Manager as defined in Exhibit D), contractors,
                                                      ---------
                                subcontractors, and all persons and entities
                                claiming through any of these persons or
                                entities.

Addresses for notices under this Lease - see also Paragraph 37:

        LANDLORD:     114 Millennium, Ltd.
                      c/o Cousins Stone LP
                      5215 N. O'Connor Blvd.,
                      Suite 1100
                      Irving, Texas 75039
                      Attention:  Tim Couch
                      Fax:        (972) 432-3650

        TENANT:       Data Return Corporation
                      222 West Las Colinas Boulevard, Suite 450E
                      Irving, Texas 75039
                      Attention:  Robert Cox, Director of Operations
                      Fax:        (972) 869-0150
                                                                          Page 2
<PAGE>

2. Leased Premises.
   ---------------

   (a) Landlord, in consideration of the Rent and the obligations of Tenant
       under this Lease, leases the Leased Premises to Tenant and Tenant leases
       the Leased Premises from Landlord, subject to the terms of this Lease.
       Landlord also grants Tenant a nonexclusive right to use the Common Areas
       and Service Areas, subject to all of the terms of this Lease.

   (b) The term Common Areas means all areas, spaces, and facilities within the
       Project made available by Landlord for the common use of Landlord,
       Tenant, other tenants in the Project, and others designated by Landlord
       using or occupying space in the Project. The Common Areas include, but
       are not necessarily limited to, walkways, sidewalks, and driveways
       necessary for access to the Buildings, parking garages at the Project
       (excluding reserved parking areas except to the extent Tenant is entitled
       to parking access cards for reserved parking under this Lease), surface
       parking areas at the Project, lobbies in the Buildings, landscaped areas,
       public corridors, public rest rooms, stairs, elevators open to the
       public, service elevators (provided that service elevators are available
       for use only by tenants of the Buildings and others designated by
       Landlord), public drinking fountains, and other similar areas and
       facilities, if any, from time to time designated by Landlord as Common
       Areas. The term Service Areas means all loading docks, loading areas, and
       all corridors that are not open to the public but which are designated by
       Landlord as being available for use by tenants in the Project and others.

   (c) The number of Rentable Square Feet (or RSF) in the Leased Premises and
       the Project is the square footage of the applicable portion of the
       Project as determined by Landlord's architect. Landlord represents to
       Tenant that the Rentable Square Feet for the Building and the Project
       have been determined in the same manner and consistently with the
       methodology used to determine the Rentable Square Feet for the Leased
       Premises.

3. Lease Term.
   ----------

   The Lease Term begins on the Commencement Date and ends on the Expiration
   Date, subject to extension as specified in Exhibit F.
                                              ---------

4. Acceptance of Leased Premises.
   -----------------------------

   The taking of possession of each Suite of the Leased Premises by Tenant for
   any purpose, whether for commencement of business or commencement of Tenant
   Finish Work (defined in Exhibit F), is conclusive evidence that Tenant: (A)
                           ---------
   accepts the Suite as suitable for the purposes for which it is leased; (B)
   accepts the Suite and the Project as being in a good and satisfactory
   condition; (C) waives any defects in the Suite and in the Project other than
   latent structural defects and defects in Building systems serving the Leased
   Premises that Tenant specifies in a notice to Landlord within 10 business
   days after taking possession of each Suite; and (D) agrees that the Rentable
   Square Feet numbers specified in this Lease are binding and conclusive for
   all purposes under this Lease. Tenant acknowledges that neither Landlord nor
   any other Landlord Party has made, and Tenant waives, any representation or
   warranty with respect to the Leased Premises or any other portion of the
   Project including,

                                                                          Page 3
<PAGE>

   without limitation, any representation or warranty with respect to the
   suitability or fitness of the Leased Premises or any other portion of the
   Project for the conduct of Tenant's business. Notwithstanding the foregoing,
   by taking of possession of any portion of the Leased Premises, Tenant shall
   not incur any liability for any violations of Applicable Laws (defined in
   Paragraph 14(a)), private restrictive covenants, or other encumbrances
   affecting the Project in existence on the Commencement Date other than
   Tenant's obligations related to the Construction Documents (defined in
   Exhibit F).
   ---------

5. Rent Payments.
   -------------

   (a) Tenant shall pay Landlord the sum of $128,934.38 when this Lease is
       executed; provided, Landlord acknowledges receipt of $11,945.28 of this
       sum under the Permittee Agreement between Landlord and Tenant dated
       November 3, 1999, covering Suites 250E and 260E (the Permittee
       Agreement), leaving a balance of $116,989.10 payable by Tenant upon
       execution of this Lease. This advance payment will be credited against
       the first installments of Minimum Rent shown in Exhibit J until the
                                                       ---------
       aggregate credit reaches $128,934.38. Except for the advance payment
       specified in the prior sentence, an installment of Minimum Rent is
       payable by Tenant in advance on the first day of each calendar month
       during the Lease Term beginning on the commencement of the Lease Term as
       specified in Exhibit J. Minimum Rent for any partial calendar month is
                    ---------
       prorated on a per diem basis.

   (b) All Rent is payable by Tenant at the times and in the amounts specified
       in this Lease in legal tender of the United States of America to Landlord
       at the following address or to any other person or at any other address
       as Landlord may from time to time designate by notice to Tenant:

                         114 Millennium, Ltd.
                         c/o Cousins Stone LP
                         P.O. Box 840913
                         Dallas, Texas 75284-0913

   (c) Rent is payable by Tenant without notice, demand, abatement, deduction,
       or setoff except as expressly specified elsewhere in this Lease. All
       amounts specified to be paid as additional Rent (other than estimated
       payments of Excess Operating Costs, which are payable as provided in
       Paragraph 9(b)) are payable by Tenant within 30 days after Tenant
       receives a demand from Landlord, which demand must include reasonable
       details concerning the amount of additional Rent being demanded. Tenant's
       obligation to pay Rent is independent of any obligation of Landlord under
       this Lease except as specified in the prior sentence. If any installment
       of Rent is not paid within 5 days after it is due, Tenant shall pay a
       late charge in an amount equal to 5% of the delinquent installment of
       Rent when it pays the delinquent installment. In addition, any Rent not
       paid when due (and which represents amounts not already specified as
       bearing interest under other provisions of this Lease) bears interest
       from the due date until the date paid at a rate (the Interest Rate) equal
       to the lesser of the highest rate allowable under applicable law or 18%
       per annum.

                                                                          Page 4
<PAGE>

6. Electricity.
   -----------

   (a) Landlord shall furnish electricity to the Leased Premises during the
       Lease Term as follows:

       (1) up to 2.25 watts per Rentable Square Foot in the Leased Premises at
           277 volts for lighting; and

       (2) up to 5.0 watts per Rentable Square Foot in the Leased Premises at
           120 volts for standard office machines.

       If Tenant wants to use any office equipment or lighting that will cause
       Tenant's electricity requirements to exceed the levels specified above or
       that will generate excess heat, Tenant must give Landlord prior notice
       specifying Tenant's excess electricity requirements and the specific
       equipment or lighting that generates excess heat. If the excess
       electricity requirements can be supplied without, in Landlord's
       reasonable opinion, overloading the existing Buildings systems, or if the
       additional equipment necessary to supply Tenant's excess electricity
       requirements can be installed without, in Landlord's reasonable opinion,
       creating a dangerous condition in the Building, Landlord shall supply
       Tenant's excess electricity requirements and Tenant shall pay Landlord
       the actual cost of supplying the excess electricity requirements,
       including all installation costs, as additional Rent. Tenant acknowledges
       that Landlord will take into account in making its decision about
       providing additional electrical capacity to Tenant Landlord's need to
       provide electrical capacity to existing and prospective (for vacant space
       in the Project) tenants. If Landlord and Tenant differ over whether
       Landlord is being reasonable in responding to a request by Tenant for
       additional electrical capacity, Landlord will submit the dispute to
       Landlord's MEP engineer, whose determination will be binding on Landlord
       and Tenant. Tenant shall pay Landlord as additional Rent 50% of the fees
       and costs charged by the MEP engineer for resolving the dispute.

   (b) If Tenant's electricity use exceeds the limits specified in Paragraph
       6(a), Landlord may, at its sole option, install separate submeter(s) for
       all or any part of the Leased Premises, and Tenant shall pay Landlord as
       additional Rent the installation cost and the cost of the electricity in
       excess of the limits specified in Paragraph 6(a).

   (c) If Tenant's electricity use exceeds the limits specified in Paragraph
       6(a) or any of Tenant's equipment or lighting generates excess heat,
       Landlord may also, at its sole option and without any obligation to do
       so, install supplemental air conditioning units in the Leased Premises to
       offset the heat-generating effect of Tenant's excess electricity usage
       and Tenant's equipment or lighting, and Tenant shall pay Landlord the
       installation cost and the cost of operation (including electricity), use,
       repair, and replacement of the supplemental air conditioning units as
       additional Rent

                                                                          Page 5
<PAGE>

   (d) The obligation of Landlord to furnish electricity is subject to the rules
       and regulations of the supplier of electricity and of any municipal or
       other governmental authority regulating the business of providing
       electricity. Landlord Parties are not liable to any Tenant Party for any
       failure or defect in the supply or character of electricity furnished to
       the Leased Premises due to any requirement, act, or omission of the
       entity supplying electricity to the Project.

   (e) Tenant shall pay to Landlord as additional Rent, without any setoff or
       deduction except as specified in this Lease, Tenant's pro rata share of
       all electricity charges incurred in the use, occupancy, and operation of
       the North and East Towers of the Project (the Buildings) and all related
       improvements and appurtenances, including the perimeter lights and
       equipment associated with the Buildings and the exterior Common Areas and
       the exterior perimeter lights for the remainder of Project. Tenant's pro
       rata share of all electricity charges incurred in the Buildings and
       related improvements and appurtenances (including electricity used for
       heating and air conditioning) is determined by multiplying (1) the Total
       Electricity Costs for the Buildings net of Submetered Power (defined
       below) and after-hours HVAC charges paid by tenants in the Buildings by
       (2) a fraction whose numerator is the number of Rentable Square Feet in
       the Leased Premises (subject to adjustment as specified in Exhibit J) and
                                                                  ---------
       whose denominator is 835,044 Rentable Square Feet (the total rentable
       area of the Buildings).

   (f) The term Total Electricity Costs for the Buildings means the total
       electricity cost charged to Landlord by the electricity provider,
       including taxes, but shall not include any administrative fee or charge
       or other cost by Landlord, subject to Paragraph 6(j). The term Submetered
       Power means all electricity in excess of the limits specified in
       Paragraph 6(a) that is separately submetered by Landlord and billed to
       tenants in the Buildings.

   (g) If Landlord at any time elects to install submeters measuring electricity
       used in the Buildings or the Leased Premises, which may include submeters
       measuring electricity used for heating and cooling the Buildings or
       Leased Premises, then Tenant's pro rata share of those actual costs will
       be based on actual use as measured by the submeters, but with any areas
       sharing a submeter being prorated on the basis that the area of the
       Leased Premises bears to the total area covered by the submeters.

   (h) Landlord shall bill Tenant for Tenant's electricity charges under this
       Paragraph monthly. Landlord shall bill Tenant for Tenant's electricity
       charge for the last full or partial month of the Lease Term as soon as
       practicable after the termination or expiration of this Lease. Tenant's
       obligation to pay the final bill and any other unpaid bills survives the
       termination or expiration of the Lease.

   (i) In lieu of the foregoing procedure, by notice to Tenant, Landlord may
       estimate, in its reasonable discretion, the monthly bill for Tenant's
       electricity charges under this Paragraph 6 and Tenant shall pay to
       Landlord the applicable monthly estimate at the same time Rent for that
       particular month is due. Landlord may adjust its estimate by notice to
       Tenant at any time during the applicable calendar year if actual
       electricity charges are substantially different from the estimate, and
       thereafter payments by Tenant under this Paragraph 6 adjust accordingly.
       No later than October 1 of each calendar

                                                                          Page 6
<PAGE>

       year thereafter, Landlord shall deliver to Tenant a statement certified
       by an authorized representative of Landlord setting out in reasonable
       detail the actual electricity charges for the prior calendar year, which
       statement shall be binding on Landlord except to the extent a corrected
       statement is provided to Tenant no later than the last day of the next
       calendar year after the calendar year in which the original statement is
       delivered or unless Tenant disputes any statement under Paragraph 9(g).
       If the estimated payments made by Tenant during the prior calendar year
       exceed Tenant's pro rata share of actual electricity charges for that
       year, Landlord shall promptly pay the difference to Tenant. If the
       estimated payments made by Tenant during the prior calendar year are less
       than Tenant's pro rata share of the actual electricity charges for that
       year, Tenant shall pay the amount of the difference to Landlord within 30
       days after delivery of any invoice therefor by Landlord accompanied by a
       statement of the actual electricity charges for that year as additional
       Rent. Tenant's and Landlord's obligations related to Tenant's pro rata
       share of the actual electricity charges survive the termination or
       expiration of this Lease.

   (j) Landlord may, in its sole discretion, elect to reduce electricity usage
       at the Project by retrofitting the Building standard electrical fixtures
       and Common Area electrical fixtures in the Project or by switching from
       electric heating to gas heating for the Project heating system and lease
       the capital improvements related to those changes. If Landlord makes
       either or both of those changes, Landlord may include the lease payments
       for the capital improvements as part of the Total Electricity Costs for
       the Buildings so long as the annual amount of lease payments included in
       Total Electricity Costs for the Buildings does not exceed the annual
       amount of the savings in electricity costs as a result of the capital
       improvements.

7. Services by Landlord.
   --------------------

   During the Lease Term, Landlord shall furnish the following services to the
   Leased Premises and other portions of the Project as specified:

   (a) air conditioning, both heating and cooling (as required by the seasons)
       for normal business operations, from 7:30 a.m. to 6:00 p.m. on weekdays
       and on Saturdays from 8:00 a.m. to 1:00 p.m., except on Holidays (as
       defined in Exhibit C) (the HVAC Standard Hours) at temperatures and in
                  ---------
       amounts as are in the sole judgment of Landlord reasonably required for
       comfortable use and occupancy under normal business operations. Normal
       business operations do not include occupancies greater than 1 person for
       each 250 Rental Square Feet of the Leased Premises on a floor-by-floor
       basis. Circulating air is not available other than through the Building's
       HVAC system. If Tenant requires HVAC services at any time other than HVAC
       Standard Hours, Landlord shall furnish after-hours HVAC service for the
       times specified in a request by Tenant received by the Manager before
       2:00 p.m. on the business day the extra usage is required. Requests
       received after that deadline will be handled in accordance with
       Landlord's Building Policies in effect at the time. Tenant acknowledges
       receipt of a copy of the current Building Policies. Landlord may make
       changes in the Building Policies that do not materially adversely affect
       Tenant's rights and/or obligations under this Lease. The changes become
       effective when a copy of the revised Building Policies is delivered to
       Tenant. Tenant shall pay Landlord as additional Rent for after-hours HVAC

                                                                          Page 7
<PAGE>

       service during the initial Lease Term $50 per hour per floor (whole or
       partial) per Building for the first floor (or the first two floors if
       they are contiguous) and $25 per hour per floor (whole or partial) per
       Building for each subsequent floor (i.e., the third floor if the first
       two floors are contiguous or the second floor if the floors are
       noncontiguous), with a 2-hour minimum. By way of example, during the
       initial Lease Term (1) the after-hours HVAC charge for service to Suite
       250E and Suite 400N would be $100 per hour, (2) the after-hours HVAC
       charge for service to Suite 250E, 260E, and 350E would be $50 per hour,
       and (3) the after-hours HVAC charge for service to Suites 250E, 350E, and
       450E (assuming Tenant exercises its expansion option under Paragraph 55)
       would be $75 per hour;

   (b) cold water (at the normal temperature of the water supply to the
       Buildings) for lavatory and toilet purposes, refrigerated water for
       drinking purposes, and hot water (from the regular Buildings supply at
       prevailing temperatures) for lavatory purposes to restrooms located in
       the core area of the Buildings only, all water service to be at supply
       points provided for general use of tenants of the Buildings through
       fixtures installed by Landlord, or by Tenant with Landlord's prior
       consent;

   (c) janitor and maid service to the Leased Premises on days other than
       Fridays, Saturdays, and Holidays;

   (d) window washing and wall cleaning as determined by Landlord in its
       reasonable discretion;

   (e) operator-less passenger elevators for ingress and egress to and from the
       floor(s) on which the Leased Premises are located (except that Landlord
       may limit the number of elevators to be in operation on Saturdays,
       Sundays, and Holidays if at least one elevator serving the Leased
       Premises is in operation) and freight elevator service in common with
       other tenants but only when scheduled through the Manager;

   (f) Common Area rest room facilities; and

   (g) electric lighting for all Common Areas and special service areas of the
       Buildings in the manner and to the extent deemed by Landlord to be
       reasonable and standard, including replacement of florescent light tubes
       in Building standard light fixtures.

   Landlord will maintain essentially the same level of services throughout the
   Lease Term as currently provided by Landlord on the Commencement Date.

   Building Standard Hours are weekdays, excluding Holidays, from 7:30 a.m. to
   6:00 p.m., Dallas, Texas time.  Landlord may lock the Buildings at all times
   other than during Building Standard Hours.  However, Landlord will provide
   Tenant with access to the Leased Premises at all times, subject to compliance
   with reasonable regulations related to entry procedures adopted by Landlord
   from time to time.

                                                                          Page 8
<PAGE>

8. Service Interruptions; Alternative Providers.
   --------------------------------------------

   (a) Landlord does not warrant that the services provided by Landlord will be
       free from any slow-down, interruption, or stoppage by governmental
       bodies, regulatory agencies, utility companies, and others supplying
       services or caused by the maintenance, repair, replacement, or
       improvement of any equipment involved in the furnishing of the services
       or caused by changes of services, alterations, strikes, lock-outs, labor
       controversies, fuel shortages, accidents, acts of God, the elements, or
       other causes beyond the reasonable control of Landlord. Landlord shall
       use due diligence to resume the services upon any slow-down,
       interruption, or stoppage.

   (b) No slow-down, interruption, or stoppage of the services may be construed
       as an eviction, actual or constructive, of Tenant or cause an abatement
       of Rent or in any manner or for any purpose relieve Tenant from its
       obligations under this Lease except as otherwise specified in this Lease.
       No Landlord Party is liable for damage to persons or property, or in
       default under this Lease, as a result of any slow-down, interruption, or
       stoppage.

   (c) Tenant may not use the services of an alternative electricity service
       provider (an ASP) rather than the utility company that is servicing the
       Project as of the date of Tenant's execution of this Lease, and no ASP
       may provide service to Tenant or to install its lines or other equipment
       within the Project, without obtaining the prior consent of Landlord.
       Landlord's consent under this subparagraph (c) is not any kind of
       warranty or representation by Landlord, including, as to the suitability
       or competence of any ASP. Further, if Landlord consents to Tenant's use
       of an ASP, then (1) all electricity services desired by Tenant shall be
       ordered and utilized at the sole expense of Tenant; (2) no Landlord Party
       has any obligation or liability with respect to the interruption or
       discontinuation, for whatever reason, of ASP service; and (3) Tenant
       shall indemnify, defend, and hold harmless all Landlord Parties for all
       claims, fines, suits, losses, costs, liabilities, demands, expenses,
       actions, and judgments (collectively, Claims) against Landlord Parties
       caused by or arising out of, either directly or indirectly, any acts or
       omissions by ASP (including those Claims resulting in any way from
       negligence or strict liability, but not the gross negligence, of any
       Landlord Party). Landlord's refusal to consent to any prospective ASP is
       not a default or breach by Landlord of its obligations under this Lease
       unless and until Landlord is adjudicated in a final and unappealable
       court decision to have acted recklessly or maliciously with respect to
       its refusal. Further, Landlord may at any time and from time to time
       during the Lease Term require Tenant to contract for electricity service
       with a different ASP or ASPs if the change in ASP will not raise
       Operating Costs (defined below) or Tenant's electricity costs for the
       Leased Premises.

   (d) Notwithstanding the provisions of Paragraphs 8(a) and (b) but subject to
       Paragraphs 21 and 22, if (i) any failure or interruption of delivery of
       electricity under Paragraph 6 or of services under Paragraph 7 is due
       solely to Landlord's negligence or intentional misconduct (Service
       Interruption) and continues for more than 5 consecutive business days
       (the Eligibility Period), (ii) it renders the Leased Premises (or a part
       of the Leased Premises) untenantable, and (iii) Tenant does not conduct
       business operations in the applicable portion of the Leased Premises,
       then Minimum Rent for the portion of the

                                                                          Page 9
<PAGE>

       Leased Premises not receiving services or electricity and not used by
       Tenant to conduct business operations shall abate commencing on the next
       day after the last day of the Eligibility Period and continuing for the
       period that the Leased Premises or the applicable portion thereof are
       rendered untenantable and are not used by Tenant to conduct business
       operations. In order to be eligible for an abatement under this Paragraph
       8(d), Tenant must provide Landlord notice (the Service Interruption
       Notice) of the date of occurrence of any Service Interruption that
       continues for more than 2 consecutive business days and the portion of
       the Leased Premises affected by the Service Interruption in which Tenant
       is not conducting business due to the Service Interruption no later than
       the third business day after the commencement of the Service
       Interruption. For the purposes of this Paragraph 8(d) only, any portion
       of the Leased Premises not receiving electricity or Landlord services
       under Paragraph 7 is deemed to be untenantable.

9. Operating Costs.
   ---------------

   (a) The term Operating Costs means those expenses (other than DCURD Taxes
       [defined below] and expenses for electricity for the Buildings) directly
       incurred in the management, operation, maintenance, repair, and security
       of the Project, including but not limited to the cost of all utilities,
       building supplies, janitorial service, maintenance, repairs (including
       repairs, refurbishments, and modifications to Common Areas of the
       Project), fire and extended coverage, commercial general liability
       insurance, and other insurance costs, all labor and employee benefit
       costs (including wages, salaries, and fees of all personnel engaged in
       the management, operation, maintenance, repair, and security of the
       Project), ad valorem taxes and assessments (both regular and special),
       costs that reduce operating expenses or are required to meet Applicable
       Laws that were not in effect on the Commencement Date, costs incurred
       with respect to Year 2000 issues, management fees, consulting fees, legal
       fees, accounting fees, and the fair market rental of the Manager's
       offices, together with payments or credits Landlord makes to any tenant
       or tenants in the Project in lieu of Landlord providing any of the
       services or paying for any of the costs in amounts not to exceed the
       actual costs of the services to Landlord. If for any time period in
       question (including the Base Year) the Project is less than 100%
       occupied, then Landlord shall extrapolate (increase) those elements of
       Operating Costs that vary based primarily on the occupancy rate of the
       Project as though the Project were 100% occupied.

       Notwithstanding anything in the foregoing definition to the contrary,
       Operating Costs do not include the following (except to the extent
       permitted by a specific exception):

             (i)    wages and salaries of employees above the grade of asset
                    manager;

             (ii)   interest, amortization, or other payments of loans by
                    Landlord (except to the extent permitted in clause (xvii)
                    below);

             (iii)  expenses incurred related to negotiations with existing and
                    prospective tenants;

                                                                         Page 10
<PAGE>

          (iv)    legal expenses, other than those directly related to service
                  contracts for the Project and those incurred by Landlord in
                  attempting to reduce or eliminate any component of Operating
                  Costs or in protecting or enhancing the value or use of the
                  Project;

          (v)     federal or state income taxes imposed on or measured by the
                  income of Landlord;

          (vi)    rents under ground leases;

          (vii)   costs incurred in selling, syndicating, financing, mortgaging,
                  or pledging Landlord's interest in the Project;

          (viii)  depreciation;

          (ix)    costs arising out of the breach by Landlord of any contract,
                  including, without limitation, penalties and interest due to
                  late payment;

          (x)     costs of correcting defects (including latent defects) in the
                  design or construction of the Project, including the
                  structural elements and the Project systems, except that
                  general maintenance and repair necessitated by or resulting
                  from ordinary wear and tear are not deemed defects;

          (xi)    costs of replacement of the structural elements of the
                  Project;

          (xii)   repairs or other work occasioned by fire, windstorm, or other
                  casualty covered or required to be covered by Landlord's
                  insurance under Paragraph 19 (other than the deductible
                  portion of the policies to the extent the costs would
                  otherwise be includable as Operating Costs) or by eminent
                  domain or a sale in lieu thereof;

          (xiii)  penalties and interest incurred due to the violation by
                  Landlord of any Applicable Laws, except in connection with a
                  good faith dispute by Landlord;

          (xiv)   costs, charges, or fees paid to subsidiaries or Affiliates
                  (defined in Paragraph 11(m)) of Landlord for services to the
                  Project to the extent that the costs of the services exceed
                  competitive costs for the services rendered by unaffiliated
                  persons or entities of similar skill, competence, and
                  experience;

          (xv)    costs of Landlord's general overhead and general
                  administrative costs and expenses that would not be chargeable
                  to Operating Costs in accordance with generally accepted
                  accounting principles, consistently applied;

          (xvi)   advertising and promotional costs and expenses other than
                  tenant newsletters and tenant parties;

                                                                         Page 11
<PAGE>

          (xvii)   expenditures for capital improvements, except for
                   amortization of the cost, together with reasonable financing
                   charges, of furnishing and installing capital investment
                   items that are: (a) primarily for the purpose of reducing
                   Operating Costs or avoiding increases in Operating Costs
                   (provided Landlord reasonably estimates at the time of
                   installing or furnishing the capital investment item that the
                   reduction in, or avoidance of, Operating Costs resulting from
                   the capital investment items will equal or exceed the
                   amortization cost of the capital items) but the amount
                   included in Operating Costs must not exceed the actual
                   reduction in Operating Costs resulting from the capital
                   investment items, (b) required by Applicable Laws not in
                   existence on the Commencement Date; and (c) repairs,
                   refurbishments, and modifications to Common Areas of the
                   Project, other than any modifications required by Applicable
                   Laws in effect on the Commencement Date. All capital costs
                   will be amortized over the useful life of the capital
                   investment item with the useful life and amortization
                   schedule being determined in accordance with generally
                   accepted accounting principles;

          (xviii)  leasing commissions;

          (xix)    rental concessions granted to specific tenants and costs
                   incurred in renovating or otherwise improving or decorating,
                   painting, or redecorating leased premises for specific
                   tenants (including Tenant) other than repairs and maintenance
                   provided for or available to tenants in general;

          (xx)     the cost or performing work or furnishing services that are
                   not available to Tenant or other tenants in the Project, for
                   which the tenants or Tenant reimburse Landlord as a separate
                   charge (other than through Operating Costs) and any other
                   costs incurred by Landlord that are subject to reimbursement
                   (other than through Operating Costs) by Tenant or other
                   tenants in the Project or third parties (including insurers);

          (xxi)    contributions to Operating Cost reserves and charitable
                   contributions; and

          (xxii)   costs incurred by Landlord in handling, removing, disposing
                   of, or replacing asbestos or asbestos-containing materials or
                   other hazardous substances in or from the Project or the
                   testing therefor.

   (b) The term Excess Operating Costs means the amount by which the Operating
       Costs for any calendar year after the Base Year exceed the Operating
       Costs for the Base Year. Landlord shall calculate Operating Costs and
       Excess Operating Costs on a Rentable Square Foot basis by dividing the
       aggregate costs by the Total Project Area. If the amount of ad valorem
       taxes and assessments for the Base Year is subsequently reduced or
       increased, then the changed amount is deemed to be the ad valorem taxes
       and assessments for the Base Year and is substituted for the original
       amount of taxes and assessments in the calculation of Operating Costs for
       the Base Year.

   (c) If there are Excess Operating Costs for any calendar year, Tenant shall
       pay to Landlord as additional Rent an amount equal to the product of the
       Excess Operating Costs (on a

                                                                         Page 12
<PAGE>

       Rentable Square Foot basis) multiplied by the number of Rentable Square
       Feet in the Leased Premises. If the amount of ad valorem taxes and
       assessments for the Base Year is changed under subparagraph (b), Tenant
       shall pay to Landlord as additional Rent any underpayment, or Landlord
       shall give Tenant an appropriate credit against future payments of Excess
       Operating Costs equal to the amount of any overpayment, in Excess
       Operating Costs resulting from the recalculation of the Operating Costs
       for the Base Year. For purposes of determining Tenant's share of Excess
       Operating Costs, Controllable Operating Costs (as defined below) for any
       calendar year shall not be increased over the amount of Controllable
       Operating Costs during the Base Year by more than 8% per year on a
       cumulative basis, compounded annually. The term Controllable Operating
       Costs means all Operating Costs except costs and expenses for taxes,
       insurance, and utilities, costs to Landlord resulting from compliance
       with any Applicable Laws (including, without limitation, all Access
       Laws), and any increases in service contract fees and expenses resulting
       from government-mandated wage increases. The term Non-Controllable
       Operating Costs shall mean all Operating Costs other than Controllable
       Operating Costs. There is no cap on Non-Controllable Operating Costs.

   (d) On or before December 1 of the Base Year and each subsequent calendar
       year, Landlord shall deliver to Tenant Landlord's reasonable estimate of
       the Excess Operating Costs for the next calendar year. Tenant shall pay
       to Landlord monthly as additional Rent, in advance on or before the first
       day in each succeeding calendar month, an amount equal to 1/12th of the
       product of the number of Rentable Square Feet in the Leased Premises
       times Landlord's estimated Excess Operating Costs for the applicable
       calendar year. Landlord may adjust its estimate by notice to Tenant at
       any time during the applicable calendar year if actual Excess Operating
       Costs are substantially different from the estimate, and thereafter
       payments by Tenant under this Paragraph adjust accordingly. The term
       calendar year includes partial calendar years.

   (e) No later than October 1 of each calendar year, Landlord shall deliver to
       Tenant a certified statement (Excess Operating Costs Statement) setting
       out in reasonable detail the actual Excess Operating Costs for the prior
       calendar year, which statement shall be binding on Landlord except to the
       extent a corrected statement is provided to Tenant no later than the last
       day of the next calendar year after the calendar year in which the
       original statement is delivered or unless Tenant disputes any statement
       under Paragraph 9(g). If the estimated payments made by Tenant during the
       prior calendar year exceed Tenant's share of actual Excess Operating
       Costs for that year, Landlord shall credit the difference against the
       next ensuing installments of estimated payments by Tenant under this
       Paragraph 9, or refund the difference to Tenant for the last calendar
       year of the Lease Term. If the estimated payments made by Tenant during
       the prior calendar year under this Paragraph are less than Tenant's share
       of the actual Excess Operating Costs for that year, Tenant shall pay the
       amount of the difference to Landlord within 30 days after delivery of any
       invoice therefor by Landlord accompanied by a statement of the actual
       Excess Operating Costs for that year as additional Rent.

   (f) As used in this Lease, (i) DCURD means Dallas County Utility and
       Reclamation District and any successor to its bond indebtedness, (ii)
       DCURD Taxes means any taxes and assessments levied against the Project by
       DCURD, and (iii) Excess DCURD Taxes

                                                                         Page 13
<PAGE>

       means the amount by which DCURD Taxes for any calendar year after the
       Base Year exceeds the DCURD Taxes for the Base Year. DCURD Taxes will be
       calculated on a Rentable Square Foot basis by dividing the DCURD Taxes by
       the Total Project Area. If there are any Excess DCURD Taxes for any
       calendar year, Tenant shall pay Landlord as additional Rent an amount
       equal to the product of the Excess DCURD Taxes (on a Rentable Square Foot
       basis) multiplied by the number of Rentable Square Feet in the Leased
       Premises. The payment and reporting of Excess DCURD Taxes shall be made
       in the same manner as Excess Operating Costs under Paragraphs 9(d) and
       9(e) above. Notwithstanding the foregoing, for purposes of determining
       Tenant's share of Excess DCURD Taxes, DCURD Taxes for each calendar year
       following the Base Year shall be calculated by multiplying the assessed
       value of the Project used by DCURD in its tax computation times the lower
       of (i) the DCURD tax rate established for the Base Year, following
       clarification and resolution of all related tax and assessment issues, or
       (ii) the actual DCURD tax rate for the year in question.

   (g) Tenant, at its expense, shall have the right to inspect, audit, and copy
       Landlord's books and records concerning the applicable Excess Operating
       Costs Statement, Excess DCURD Taxes statement, and/or actual electricity
       charges statement at Manager's offices during normal office hours within
       180 days after the date of the Excess Operating Costs Statement, Excess
       DCURD Taxes statement, and/or actual electricity charges statement by
       giving Landlord at least 30 days' prior notice. Any audit by Tenant is
       subject to the following:

       (1)  No audit may be conducted if:

            (A)  any other tenant of the Building has conducted an audit for the
                 same calendar year using a nationally recognized public
                 accounting firm and Landlord delivers a copy of the other
                 tenant's audit to Tenant within 10 days after Landlord receives
                 Tenant's notice requesting the audit; or

            (B)  Tenant is in default under this Lease at the time Tenant
                 delivers its notice to Landlord requesting the audit or at the
                 time the audit would be conducted.

            No subtenant or assignee (other than an assignee who is an Affiliate
            of Tenant) may conduct an audit under this subparagraph or
            otherwise.

       (2)  If Tenant retains a third party (the Auditor) to audit any Excess
            Operating Costs Statement, the Auditor must be a nationally
            recognized accounting firm that is not being compensated by Tenant
            on a contingent fee basis or other "savings" based fee structure.
            Prior to conducting an audit, Tenant and any Auditor must execute
            Landlord's standard form of confidentiality agreement relating to
            the audit.

       (3)  Tenant may not be in Manager's offices for more than a total of 5
            business days. Tenant shall make reasonable efforts to minimize any
            disruption to Landlord's business while in Manager's offices.
            Landlord and Manager shall use commercially reasonable efforts to
            cooperate with Tenant and the Auditor.

                                                                         Page 14
<PAGE>

        (4)   Tenant shall deliver a copy of the audit to Landlord within 30
              days after Tenant's auditor completes its examination of
              Landlord's records. If Tenant disputes any Excess Operating Costs
              Statement, Excess DCURD Taxes statement, and/or actual electricity
              charges statement as a result of its audit and Landlord does not
              contest the accuracy of Tenant's dispute within 15 business days
              after Landlord's receipt of Tenant's dispute notice, Landlord
              shall reimburse Tenant the amount of any overpayment, or Tenant
              shall pay Landlord the amount of any underpayment, together with
              interest thereon from the date of the dispute notice until paid at
              the Interest Rate.

10. Security Deposit
    ----------------

    (a) Tenant shall pay the Security Deposit to Landlord upon execution of this
        Lease as security for the performance by Tenant of its obligations under
        this Lease. The Security Deposit may be commingled with Landlord's
        general funds, is not held in trust for Tenant, does not bear interest,
        and is not an advance payment of Rent or a measure of Landlord's damages
        for a default by Tenant. If Tenant defaults in the performance of any of
        its obligations under this Lease, Landlord may, without prejudice to any
        other remedy, use the Security Deposit to the extent necessary to make
        good any arrearages in Rent or any other sum for which Tenant is in
        default and any other damage, injury, expense, or liability caused to
        Landlord by the default. If Landlord so applies any part of the Security
        Deposit, Tenant shall pay to Landlord the amount necessary to restore
        the Security Deposit to its original amount.

    (b) Landlord shall return any remaining balance of the Security Deposit
        (after deduction of any unpaid Rent or other charges owing by Tenant
        under this Lease) to Tenant within 60 days after the later to occur of
        (1) the termination or expiration of this Lease or (2) surrender by
        Tenant of possession of the Leased Premises to Landlord in accordance
        with the requirements of Paragraph 25.

    (c) If Landlord assigns its interest in the Leased Premises, Landlord shall
        assign the Security Deposit to the assignee. Landlord has no further
        liability for the return of the Security Deposit after the assignment
        and Tenant shall look solely to the assignee for the return of the
        Security Deposit. Tenant may not assign or encumber or attempt to assign
        or encumber the Security Deposit. Landlord and its successors and
        assigns are not bound by any actual or attempted assignment or
        encumbrance of the Security Deposit by Tenant.

11. Assignment and Subletting.
    -------------------------

    (a) Tenant may not, without Landlord's prior reasonable consent, except as
        specified in Paragraph 11(l) below: (1) assign or transfer this Lease or
        any interest therein; (2) permit any assignment of this Lease or any
        interest therein by operation of law; (3) sublet the Leased Premises or
        any part thereof; (4) grant any license, concession, or other right of
        occupancy of any portion of the Leased Premises; (5) mortgage, pledge,
        or otherwise encumber its interest in this Lease; or (6) permit the use
        of the Leased Premises by any parties other than Tenant and its
        employees except that Tenant may allow one or more of the entities (the
        Permitted Temporary Occupants) listed in Exhibit I to occupy
                                                 ---------

                                                                         Page 15
<PAGE>

        portions of the Leased Premises on a temporary basis if the occupancy
        does not require any alterations to the Leased Premises and Tenant
        receives no more than nominal consideration from the occupying entity.
        In no event shall the following be considered as suitable assignees or
        sublessees under this Lease: (i) any governmental body, agency or bureau
        of the United States, any state, county, municipality or any subdivision
        thereof; (ii) any foreign government or subdivision thereof; (iii) any
        health care professional or health care service organization; (iv) any
        school or similar organization; (v) any employment agency; (vi) any
        radio, television or other communication station; (vii) any restaurant
        or similar establishment offering food or beverages for consumption on
        or off site; (viii) any retailer offering retail services from the
        Leased Premises; (ix) any entity from whom Landlord has received an
        inquiry about space in the Project within the 90-day period prior to
        Tenant's request for approval of a sublease or assignment or with whom
        Landlord is then negotiating (provided the entity shall not be
        considered unsuitable if Landlord does not have comparable space in the
        Project available for lease); (x) any existing tenant in the Project;
        (xi) any entity whose proposed use would violate any exclusive use
        granted by Landlord to another Tenant in the Project; and (xi) any
        entity that has been involved in any actual or threatened legal disputes
        with Landlord, Manager, or any Landlord Affiliate. Landlord's consent to
        any assignment, subletting, or reorganization is not a waiver of
        Landlord's right to approve or disapprove any subsequent assignment,
        subletting, or reorganization.

    (b) Tenant and any guarantor of Tenant's obligations under this Lease
        (Guarantor, whether one or more) remain jointly and severally liable for
        the payment of Rent and performance of all other obligations under this
        Lease after any assignment or subletting, during the initial Lease Term
        and any renewal or extension of the Lease Term. If Tenant is a
        partnership, Tenant, Guarantor, and the general partners of Tenant prior
        to its reorganization remain jointly and severally liable for the
        payment of Rent and performance of all other obligations under this
        Lease after any reorganization.

    (c) Notwithstanding the giving by Landlord of its consent to any sublease or
        assignment with respect to the Leased Premises, no sublessee or assignee
        (other than an assignee who is an Affiliate of Tenant) may exercise any
        renewal options, expansion options, rights of first notice, or similar
        expansion rights under this Lease, except that a non-Affiliate assignee
        may exercise such rights in accordance with a separate written agreement
        entered into directly between the assignee and Landlord, provided Tenant
        agrees at such time to continue to be liable for the performance of all
        obligations hereunder, as increased or otherwise affected by the
        exercise of the expansion rights. Tenant may not exercise any renewal
        options, expansion options, rights of first notice, or similar rights
        under this Lease if Tenant has assigned any portion of its interest in
        this Lease to any entity other than to an Affiliate assignee.

                                                                         Page 16
<PAGE>

    (d) If an Event of Default (defined in Paragraph 27) occurs while the Leased
        Premises or any part thereof are assigned or sublet, Landlord, in
        addition to any other remedies under this Lease or provided by law, may
        at its option collect directly from the assignee or sublessee all rents
        payable to Tenant under the assignment or sublease and apply the rent
        against any sums due to Landlord under this Lease. Tenant authorizes and
        directs any assignee or sublessee to make payments of rent directly to
        Landlord upon receipt of notice from Landlord. No direct collection of
        rent by Landlord from any assignee or sublessee is a novation or a
        release of Tenant or Guarantor from the performance of their obligations
        under this Lease or under any guaranty executed by Guarantor. Receipt by
        Landlord of rent from any assignee, sublessee, or occupant of the Leased
        Premises is not a waiver of the covenant against assignment and
        subletting or a release of Tenant or Guarantor.

    (e) If Tenant wants to assign or sublease all or part of the Leased
        Premises, it shall deliver a notice to Landlord specifying the name of,
        financial information (for proposed assignees only, not for proposed
        sublessees) for, and the nature of the business of the proposed assignee
        or sublessee, and the proposed effective date of the assignment or
        sublease (which date may not be later than 6 months after Tenant's
        notice is delivered to Landlord). Tenant may not (i) deliver more than 8
        notices to Landlord under this Paragraph 11(e) during the Lease Term (it
        being understood that multiple requests made at the same time only count
        as 1 request under this Paragraph 11(e)) or (ii) assign or sublease all
        or any part of the Leased Premises at any time when Tenant is in default
        under this Lease, whether or not an Event of Default has occurred.

    (f) Landlord has a period of 20 days from receipt of Tenant's notice to
        notify Tenant that Landlord elects, in Landlord's sole discretion, to:

        (1) terminate this Lease as to the space that is the subject of Tenant's
            notice as of the date specified by Tenant, subject to Paragraph
            11(g);

        (2) consent to the assignment or sublease; or

        (3) refuse to consent to Tenant's assignment or sublease of that space
            and to continue this Lease in effect.

        If Landlord does not notify Tenant of Landlord's election within the 20-
        day period, Landlord is deemed to elect option (3) but Tenant may give
        Landlord notice within 5 days after the expiration of the 20-day period,
        with the envelope and notice marked URGENT, requesting notice of
        Landlord's election and, if Landlord does not give Tenant notice of its
        election within 10 days after Landlord's actual receipt of Tenant's
        URGENT notice, Landlord is deemed to elect option (2).

    (g) Landlord may exercise its right of termination under Paragraph 11(f)
        only if:

        (1) Tenant proposes to assign its interest in this Lease to any entity
            other than an Affiliate of Tenant; or

                                                                         Page 17
<PAGE>

        (2) Tenant proposes to sublease (A) 90% or more of the portions of the
            Leased Premises on any floor of a Building for a term that expires
            within 90 days of the Expiration Date, in which event Landlord may
            recapture all of the Leased Premises on the floor in question, or
            (B) the proposed sublease, together with any other existing
            subleases, constitutes an aggregate of 50% or more of the Leased
            Premises, in which event Landlord may recapture all of the Leased
            Premises covered by the proposed sublease.

    (h) If the rent (i.e., the aggregate of all amounts) payable to Tenant by
        any approved sublessee is greater than the Rent, Tenant shall pay
        Landlord 65% of the excess rent within 10 days after Tenant's receipt
        thereof from the sublessee.

    (i) As a condition to the effectiveness of each assignment or subletting,
        Tenant shall pay to Landlord its reasonable administrative and legal
        costs in connection therewith, not to exceed $1,000.

    (j) Any attempted assignment or sublease by Tenant in violation of the terms
        of this Paragraph 11 is void.

    (k) Tenant may not enter into any sublease, license, concession, or other
        agreement for any use, occupancy, or utilization of the Leased Premises
        that provides for a rental or other payment for use, occupancy, or
        utilization based in whole or in part on the net income or profits
        derived by any person from the premises so leased, used, occupied, or
        utilized.

    (l) Tenant may, without the prior consent of Landlord and without Paragraphs
        11(f), 11(g), 11(h), and 11(i) being applicable, sublet all or any part
        of the Leased Premises to an Affiliate of Tenant, or assign this Lease
        to an Affiliate of Tenant, if (1) Tenant provides Landlord notice of the
        sublease or an original of the assignment within 10 days after its
        execution and (2) the transaction was not entered into as a subterfuge
        to avoid the obligations and restrictions of this Lease. Tenant and
        Guarantor remain jointly and severally liable for the payment of Rent
        and performance of all other obligations under this Lease after any
        assignment or subletting to an Affiliate of Tenant.

    (m) An Affiliate of an entity is any entity that acquires all or part of the
        entity in question, or that is acquired in whole or in part by the
        entity in question, or which controls, is controlled by, or is under
        common control with, directly or indirectly, the entity in question. For
        purposes of this subparagraph, control means the possession, directly or
        indirectly, of the power to direct or cause the direction of the
        management and policies of an entity, whether through the ownership of
        voting securities or by contract or otherwise.

    (n) If Landlord exercises its termination right set forth in subparagraph
        11(f)(1) above as to less than all of the Leased Premises, Landlord
        shall prepare, and Landlord and Tenant shall promptly execute and
        deliver, an appropriate amendment to this Lease to reflect proportionate
        reductions in Minimum Rent, the Rentable Square Feet in the Leased
        Premises, parking access cards, etc.

                                                                         Page 18
<PAGE>

12. Repair and Maintenance.
    ----------------------

    (a) Tenant shall keep the Leased Premises [including, without limitation,
        Standard Improvements and Tenant Improvements (both as defined in
        Exhibit F)] and all fixtures installed by or on behalf of Tenant in good
        ---------
        and tenantable condition. Tenant shall promptly make all necessary non-
        structural repairs and replacements to its fixtures and Tenant
        Improvements, all at Tenant's expense, with the reasonable approval of
        Landlord. All repairs and replacements must be equal in quality and
        class to the original work. Without diminishing this obligation of
        Tenant, if Tenant fails to commence any repairs and replacements within
        15 days after notice from Landlord or to thereafter diligently complete
        the repairs and replacements, Landlord may at its option make the
        repairs and replacements and Tenant shall pay Landlord as additional
        Rent the actual costs incurred by Landlord plus an administrative fee
        equal to 5% of the costs.

    (b) Subject to Paragraph 24,Tenant shall pay the cost of repairs and
        replacements due to damage or injury to the Project or any part thereof
        caused by any Tenant Party or by any malfunction or misuse of any
        equipment installed by or on behalf of Tenant. This amount is payable by
        Tenant to Landlord as additional Rent, plus interest at the Interest
        Rate from the date of payment by Landlord until paid by Tenant. If
        Tenant requests Landlord to perform any maintenance or repairs to the
        Leased Premises over and above the services required to be performed by
        Landlord under Paragraph 7, Tenant shall pay the actual cost thereof,
        plus an administrative fee equal to 5% of the actual cost thereof, to
        Landlord as additional Rent.

    (c) Landlord shall (to the extent the repair is not the obligation of Tenant
        under this Lease) keep and maintain the foundation, exterior walls,
        exterior windows, roof, Building systems, and other structural elements
        and Common Areas and Service Areas of the Project in good condition and
        repair as reasonably determined to be necessary by Landlord, consistent
        with the condition existing on the Commencement Date.

13. Alterations and Additions by Tenant.
    -----------------------------------

    (a) Tenant may not make or permit any alterations, improvements, or
        additions in or to the Leased Premises or the Project without Landlord's
        prior reasonable consent. All alterations, additions, and improvements
        made to, or fixtures or other improvements placed in or upon, the Leased
        Premises, whether temporary or permanent in character, by either party
        (except only Tenant's movable trade fixtures, office furniture, and
        equipment) are a part of the Project and are the property of Landlord
        when they are placed in the Leased Premises without compensation to
        Tenant. Alterations, improvements, and additions in and to the Leased
        Premises requested by Tenant must be made in accordance with complete
        and accurate plans and specifications and construction documents
        [including, without limitation, complete mechanical, electrical and
        plumbing (MEP) requirements, if applicable] prepared by Tenant and
        reasonably approved in advance by Landlord. Landlord shall approve or
        disapprove any requested alterations, improvements, or additions within
        14 days after Tenant's delivery of complete plans and specifications
        therefor. Any disapproval by Landlord must specify the reasons for the
        disapproval. If Landlord does not approve or disapprove any plans and
        specifications submitted to Landlord within the 14-day period, Landlord
        is deemed to

                                                                         Page 19
<PAGE>

        approve the plans and specifications. All work must be performed at
        Tenant's expense either by Landlord or, at Tenant's option, by Tenant
        through contractors and subcontractors reasonably approved in advance by
        Landlord. If the work is not performed by Landlord, then all work
        performed by Tenant's contractors and subcontractors is subject to the
        following conditions:

        (1) Each contractor and subcontractor must deliver evidence reasonably
            satisfactory to Landlord that the insurance specified on Exhibit D
                                                                     ---------
            is in force prior to commencing work.

        (2) Tenant shall ensure that all workers cooperate with Project
            personnel and comply with all Project Rules and Regulations.

        (3) Tenant must deliver to Landlord evidence that Tenant has obtained
            all necessary governmental permits and approvals for the
            improvements or alterations prior to starting any work.

        (4) All construction must be done in a good and workmanlike manner and
            is subject to reasonable approval by Landlord during and after
            construction to determine compliance with the approved plans and
            specifications and construction documents.

        (5) Recordable lien releases from each contractor and subcontractor must
            be submitted to Landlord within 30 days after completion of the work
            performed by the contractor or subcontractor.

        (6) Within 30 days after completion of any improvements or alterations,
            Tenant, at its cost, shall deliver to Landlord 2 reproducible copies
            of "as-built" plans and specifications (1/8" scale) for each floor
            where alterations or improvements were made.

        All changes to the plans and specifications and construction documents
        are also subject to Landlord's prior reasonable approval.

    (b) Tenant must use Landlord's fire protection contractor and must either
        (1) use Landlord's MEP engineer to prepare the MEP portions of the plans
        and specifications and construction documents, or (2) reimburse the cost
        of one review by Landlord's MEP engineer of the plans and specifications
        and the construction documents, not to exceed $0.15 per rentable square
        foot of the area of the Leased Premises covered by the review. Landlord
        shall cause its fire protection contractor and MEP engineer to perform
        the work for Tenant at Landlord's contracted rates.

    (c) All alterations and improvements by Tenant must comply with all
        Applicable Laws. Tenant and its consultants must coordinate any
        alterations or additions relating to compliance with the Americans With
        Disabilities Act of 1990 (as amended), the Texas Architectural Barriers
        Act (as amended) [Tex. Rev. Civ. Stat. Ann. Art. 9102], and any similar
        existing or future law, rule or regulation relating to access by
        disabled persons to the Leased Premises or the Project (collectively,
        Access Laws) with Landlord and Landlord's Access Law compliance plan for
        the Project in preparing the plans and

                                                                         Page 20
<PAGE>

        specifications and construction documents. Neither Landlord's approval
        of Tenant's plans and specifications for the alterations or improvements
        nor Landlord's acceptance of Tenant's as-built plans is a confirmation
        or agreement by Landlord that the improvements and alterations comply
        with Applicable Laws. Tenant is not responsible for Access Law
        compliance obligations in areas of the Project outside the Leased
        Premises (or for Access Law compliance related to core area rest rooms
        on single tenant floors, even though those core area rest rooms are part
        of the Leased Premises on those single tenant floors) triggered by any
        work by Tenant in the Leased Premises as long as Tenant is not using the
        Leased Premises as a public accommodation.

    (d) Within 30 days after Tenant installs any telephone or data cables in the
        Leased Premises, Tenant, at its cost, shall deliver to Landlord 2
        reproducible copies of "as-built" plans and specifications (1/8" scale)
        showing the location of the telephone and data cables.

    (e) As between Landlord and Tenant, for purposes of the insurance
        requirements of Paragraph 18, Tenant has an insurable interest in all of
        the Tenant Improvements and alterations made by Tenant in the Leased
        Premises; provided that, except as otherwise provided in this Lease, all
        of the Tenant Improvements and alterations shall be surrendered to
        Landlord with the Leased Premises upon the expiration or earlier
        termination of the Lease as set forth in Paragraph 26.

    (f) Whenever (i) Landlord's approval of plans and specifications is required
        under this Paragraph 13 or under Exhibit F, (ii) Tenant disputes whether
                                         ---------
        Landlord's approval or disapproval is reasonable, and (iii) the approval
        involves changes to any structural elements of the Project or to any
        portions of the Building systems that serve more than one tenant,
        Landlord shall submit the dispute to Landlord's MEP engineer. The
        decision of Landlord's MEP engineer will be binding on Landlord and
        Tenant. If the MEP engineer decides that Landlord was acting reasonably,
        Tenant shall pay all fees and costs charged by the MEP engineer. If the
        MEP engineer decides that Landlord was not acting reasonably, Landlord
        shall pay all fees and costs charged by the MEP engineer.

14. Use and Occupancy.
    -----------------

    (a) The Leased Premises may be used and occupied by Tenant only for general
        business offices and incidental uses (including, without limitation,
        customer support operations, computer operations, and employee break
        rooms) and for no other purpose without Landlord's prior consent, in its
        sole discretion. Tenant shall use and maintain the Leased Premises in a
        clean, careful, safe, and proper manner and shall comply with all laws,
        ordinances, orders, rules, and regulations of all governmental bodies
        (state, federal, and municipal) applicable to or having jurisdiction
        over the use and occupancy of the Leased Premises, including without
        limitation, all applicable environmental laws, and the Access Laws
        (those laws, ordinances, orders, rules, decisions, and regulations, and
        existing and future amendments thereto, being collectively called
        Applicable Laws), subject to the last sentence of Paragraph 13(c).

                                                                         Page 21
<PAGE>

    (b) Tenant may not deface or injure the Leased Premises or the Project or
        any part thereof or overload the floors of the Leased Premises. Tenant
        may not commit waste or permit waste to be committed or cause or permit
        any nuisance on or in the Leased Premises or the Project. Subject to
        Paragraph 24, Tenant shall pay Landlord as additional Rent the cost to
        repair any damage to the Leased Premises or to any other part of the
        Project caused by any negligence or willful act or any misuse or abuse
        (whether or not the misuse or abuse results from negligence or willful
        acts) by any Tenant Party.

    (c) Tenant may not use or allow the Leased Premises to be used for any
        purpose prohibited by any Applicable Law, or by any restrictive
        covenants applicable to the Project on the Commencement Date, or as a
        manned express mail pick up center for delivery services like Airborne
        and Federal Express, or for a mini-bank or bank. Tenant may not sell,
        purchase, or give away, or permit, except with Landlord's prior
        approval, the sale, purchase, or gift of food in any form (other than
        food ordered in for training sessions, meetings, and/or employee
        consumption) by or to any Tenant Party or any other parties at the
        Leased Premises or the Project. Tenant shall conduct its business and
        occupy the Leased Premises and control all Tenant Parties so as not to
        create any nuisance or interfere with, annoy, or disturb any other
        tenants in the Project or Landlord in its management of the Project and
        so as not to injure the reputation of the Project.

    (d) Tenant may not erect, place, or allow to be placed any sign, advertising
        matter, stand, booth, or showcase in or upon the doorsteps, vestibules,
        halls, corridors, doors, walls, windows, or pavement of the Project
        visible outside the Leased Premises (except for lettering on the door or
        doors to the Leased Premises as allowed by the Project Rules and
        Regulations attached as Exhibit C) without the prior consent of
                                ---------
        Landlord.

    (e) Tenant may not use or allow or permit the Leased Premises to be used in
        any way or for any purpose that:

        (1) Landlord deems hazardous on account of the possibility of fire or
            other casualty;

        (2) increases the rate of fire or other insurance for the Project or its
            contents or in respect of the operation of the Project; or

        (3) renders the Project uninsurable at normal rates by responsible
            insurance carriers authorized to do business in the State of Texas
            or renders void or voidable any insurance on the Project.

        If insurance premiums are increased solely because of Tenant's use of
        the Leased Premises, then, in addition to any other remedies Landlord
        may have, Tenant shall pay the amount of the increase to Landlord as
        additional Rent.

15. Mechanics' Liens - Tenant's Obligations.
    ---------------------------------------

    Tenant may not cause or permit any mechanic's or materialman's lien to be
    placed upon Landlord's interest in the Project or the Leased Premises or any
    part thereof or against Landlord's interest under this Lease by any
    contractor, subcontractor, laborer, materialman or supplier performing any
    labor or furnishing any materials to Tenant for any improvement,

                                                                         Page 22
<PAGE>

    alteration, or repair of or to the Leased Premises, the Project, or any part
    thereof. If any lien is filed on Landlord's interest or Tenant's interest in
    the Leased Premises, Tenant shall cause the same to be discharged of record,
    by bonding or otherwise, within 20 days after Tenant receives notice of the
    filing. If Tenant does not discharge the lien within the 20-day period,
    then, in addition to any other right or remedy of Landlord, Landlord may,
    but is not obligated to, discharge the lien by paying the amount claimed to
    be due or by procuring the discharge of the lien by deposit in court or
    bonding. Any amount paid by Landlord relating to any lien not caused by a
    Landlord Party, and all reasonable legal and other expenses of Landlord,
    including reasonable legal fees, costs, and expenses in defending any action
    or in procuring the discharge of any lien, with interest thereon at the
    Interest Rate from date of payment by Landlord until paid by Tenant, is
    payable by Tenant to Landlord as additional Rent.

16. Limitations on Liability of Landlord Parties; Waiver.
    ----------------------------------------------------

    (a) To the fullest extent permitted by law, Tenant, on its behalf and on
        behalf of all Tenant Parties, waives all Claims (in law, equity, or
        otherwise) against all Landlord Parties arising out of, knowingly and
        voluntarily assumes the risk of, and agrees that Landlord Parties are
        not liable to any Tenant Parties for any of the following even if the
        Claims are caused solely or in part by the negligence or strict
        liability, but not the gross negligence, of any Landlord Party:

        (1) any injury or damage to person or property (including the resulting
            loss of use, economic losses and consequential or resulting damages
            of any kind from any cause) due to the condition or design of, or
            any defect in, the Leased Premises or Project that exists now or
            occurs in the future;

        (2) any injury or damage to person or property (including the resulting
            loss of use, economic losses, and consequential or resulting damages
            of any kind from any cause) due to the Leased Premises or Project or
            related improvements or appurtenances being out of repair, or
            defects in or failure of pipes or wiring, or backing up of drains,
            or the bursting or leaking of pipes, faucets, and plumbing fixtures,
            or gas, water, steam, electricity, or oil leaking, escaping, or
            flowing into the Leased Premises;

        (3) any loss or damage caused by the acts or omissions of other tenants
            in the Project or of any other persons; or

        (4) any loss or damage to property or person occasioned by theft, fire,
            act of God, public enemy, injunction, riot, insurrection, war, court
            order, requisition, order of governmental authority, and any other
            cause beyond the control of Landlord.

        Landlord's obligations under Paragraph 17(b) are not modified or reduced
        by the waivers in this Paragraph 16(a).

    (b) Notwithstanding the foregoing or anything else to the contrary contained
        in this Lease, the liability of Landlord to any Tenant Party for any
        default or indemnity by Landlord under this Lease is limited to the
        interest of Landlord in the Project. No Landlord Party

                                                                         Page 23
<PAGE>

        has any personal liability for any amounts payable or obligations
        performable by Landlord under this Lease.

    (c) The provisions of this Paragraph 16 survive the expiration or earlier
        termination of this Lease.

17. Indemnification.
    ---------------

    (a) Subject to Paragraph 24, Tenant shall indemnify, defend, and hold all
        Landlord Parties harmless from all Claims of every kind and character
        (including those Claims resulting solely or in part from negligence or
        strict liability, but not the gross negligence, of any Landlord Party)
        arising out of or relating (directly or indirectly) to the following:

        (1) any breach or default in performance of any obligation on Tenant's
            part to be performed under this Lease, whether before or during the
            Lease Term or after its expiration or earlier termination;

        (2) any act, omission, negligence, or misconduct in the Leased Premises
            of any Tenant Party or of any other person entering upon the Leased
            Premises under or with the express or implied invitation or
            permission of Tenant;

        (3) any alterations, activities, work, or things done, permitted,
            allowed, or suffered by Tenant in, at, or about the Leased Premises,
            including the violation by any Tenant Party of any law, ordinance,
            or governmental order of any kind; and

        (4) the occupancy or use by any Tenant Party of the Leased Premises.

    (b) Landlord shall indemnify, defend, and hold Tenant harmless from all
        Claims (including those claims resulting solely or in part from the
        negligence or strict liability, but not the gross negligence, of tenant
        (i) arising because of any bodily injury, death or damage to property
        (excluding damages to the personal property of a Tenant Party) occurring
        in or resulting from any occurrence during the Lease Term in the Common
        Areas of the Project; or (ii) arising out of any breach or default in
        performance of any obligation on Landlord's part to be performed under
        this Lease, whether before or during the Lease Term or after its
        expiration or earlier termination. The provisions of this Paragraph
        17(b) control if there is a conflict with the provisions of Paragraph
        16(a).

    (c) If any employee (full-time, part-time, or temporary) of any Tenant Party
        suffers an injury at the Project, Tenant shall use reasonable efforts to
        cause the injured employee to exhaust all rights under the applicable
        Workers' Compensation Laws before any claim arising from the injury is
        asserted against any Landlord Party.

    (d) The provisions of this Paragraph 17 survive the expiration or earlier
        termination of this Lease.

    (e) The indemnification provisions of this Paragraph 17 may not be construed
        or interpreted as in any way restricting, limiting, or modifying
        Tenant's or Landlord's insurance or other

                                                                         Page 24
<PAGE>

        obligations under this Lease and are independent of Tenant's and
        Landlord's insurance and other obligations under this Lease.

18. Tenant's Insurance.
    ------------------

    (a) Tenant shall, at its expense, maintain at all times during the Lease
        Term (and prior to the Lease Term with respect to activities of Tenant
        under this Lease at the Project), insurance as set forth below:

        (1)  Commercial General Liability Insurance (1986 ISO Form or its
             replacement) written on an "occurrence" basis with respect to the
             business carried on, in or from the Leased Premises and Tenant's
             use and occupancy of the Leased Premises (including contractual
             liability) in an amount not less than $1,000,000 per occurrence and
             $2,000,000 general aggregate per location for bodily injury and
             property damages combined (or with increased limits as may be
             required from time to time by Landlord by giving notice to Tenant)
             and without any deductibles;

        (2)  Workers' Compensation Insurance, including at least
             $1,000,000/1,000,000/1,000,000 Employers Liability Insurance;

        (3)  Excess/Umbrella Liability Insurance, applying on at least a
             "following form" (or primary) basis, with a minimum limit of
             $3,000,000 each Occurrence and Aggregate, where applicable;
             provided that Tenant will not be required to provide this coverage
             if it increases the aggregate limit on its Commercial General
             Liability Insurance policy to at least $3,000,00; and

        (4)  The equivalent of "ISO Special Form" Property Insurance, including
             but not limited to, coverage for:

             A.  All office furniture, trade fixtures, office equipment,
                 merchandise, and all other items of Tenant's property in, on,
                 at, or about the Leased Premises and the Project, including
                 property installed by, for, or at the expense of Tenant;

             B.  Tenant Improvements; and

             C.  Except for Standard Improvements, all other improvements,
                 betterments, alterations, and additions to the Leased Premises.

             Tenant's Property Insurance must also fulfill the following
             requirements:

                 (AA)  Include Landlord as an additional insured but only as to
                       Tenant Improvements and other alterations or improvements
                       to the Leased Premises;

                 (BB)  Include an agreed amount endorsement (with coinsurance
                       waived) for not less than 100% of the full replacement
                       cost (new without deduction for depreciation) of the
                       covered items and property; and

                                                                         Page 25
<PAGE>

                 (CC)  Include a deductible no greater than $25,000 for each
                       loss.


    (b) Tenant's policies must be written by an insurance company or companies
        with a current A.M. Best's rating of A-IX or better and be admitted to
        do business in the State of Texas. Landlord and Manager must be named as
        additional insureds without restriction under the liability and property
        policies. Tenant shall obtain an endorsement from each insurance company
        agreeing to notify Landlord in writing at least 30 days prior to
        cancellation, non-renewal, or material reduction of the coverage.

    (c) Tenant shall deliver to Landlord duly executed certificates of insurance
        (Acord Form 27, modified as necessary) and additional insured
        endorsements reasonably satisfactory to Landlord prior to occupying any
        part of the Leased Premises, and on an annual basis thereafter. If
        Tenant fails to comply with these insurance requirements and does not
        cure the failure within 10 business days after receipt of notice from
        Landlord of the failure, Landlord may obtain the required insurance and
        Tenant shall pay to Landlord as additional Rent the premium cost thereof
        plus interest at the Interest Rate from the date of payment by Landlord
        until paid by Tenant.

19. Landlord's Insurance.
    --------------------

    Landlord shall carry, or cause to be carried: (A) Commercial General
    Liability Insurance with limits of liability of not less than $1,000,000
    each occurrence, single limit Bodily Injury and Property Damage combined;
    (B) the equivalent of "ISO Special Form" Property Insurance insuring the
    Project for the full replacement value thereof, with a deductible not to
    exceed $100,000 for each loss, excluding Tenant Improvements and Tenant's
    merchandise, trade fixtures, furnishings, equipment, personal property, and
    any alterations or additions made by Tenant; and (C) business interruption
    insurance covering the Buildings, with a coverage term of at least 1 year.
    Landlord may carry its insurance under blanket policies.

20. Rights Reserved by Landlord.
    ---------------------------

    Landlord reserves the following rights, exercisable without notice (except
    as specified below) and, subject to Paragraph 17(b)(i), without liability to
    any Tenant Party for damage or injury to property, persons, or business and
    without effecting an eviction, constructive or actual, or disturbance of
    Tenant's use or possession or giving rise to any claim for set-off or
    abatement of Rent unless Tenant's access to or use of the Leased Premises or
    the parking garage at the Project is materially adversely affected:

    (a) To change the Building's or the Project's name or street address after
        using commercially reasonable efforts to give Tenant at least 30 days
        notice of the change.

    (b) To install, affix, and maintain any signs on the exterior and interior
        of the Project.

    (c) To designate and approve, prior to installation, all types of window
        shades, blinds, drapes, awnings, window ventilators, and similar
        equipment, and to control all internal lighting that is visible from the
        exterior of the Project.

                                                                         Page 26
<PAGE>

    (d) To designate, restrict, and control all sources within the Project where
        Tenant may obtain ice, drinking water, towels, toilet supplies,
        catering, food and beverages, and like or other services on the Leased
        Premises and, in general, the exclusive right to designate, limit,
        restrict, and control any business and any service in or to the Project
        and its tenants.

    (e) To enter upon the Leased Premises at reasonable hours (provided Landlord
        uses commercially reasonable efforts to give reasonable prior notice to
        Tenant except for entry to provide janitorial services or in an
        emergency) to inspect, clean, or make necessary (under Applicable Laws
        or in connection with the operation of the Building) repairs or
        alterations to the Leased Premises (but without any obligation to do so,
        except as expressly specified in this Lease), to make repairs or
        alterations to any part of the Buildings or the Buildings systems
        (including adjacent premises), to show the Leased Premises to
        prospective lenders and purchasers, and, during the last 12 months of
        the Lease Term, as may have been extended hereunder, to show the Leased
        Premises to prospective tenants at reasonable hours and, if the Leased
        Premises are vacant, to clean them. Landlord shall use commercially
        reasonable efforts to exercise its rights under this Paragraph 20(e) in
        a way that minimizes interference with Tenant's operations in and access
        to the Leased Premises or access to the parking garage at the Project
        except in emergencies.

    (f) To retain at all times, and to use in appropriate instances, keys to all
        doors within and into the Leased Premises. No locks may be changed or
        added without the prior reasonable consent of Landlord. Subject to
        compliance with Paragraph 13, Tenant shall have the right to install an
        electronically controlled access system on all exterior doors of the
        Leased Premises and record all entries into the Leased Premises but
        Tenant's system must not interfere with Landlord's existing electronic
        access system for the Project and Tenant must provide Landlord with an
        adequate supply of access cards for Landlord, Manager, and Landlord's
        janitorial provider. Tenant shall have the right to, and shall upon
        request by Landlord, remove its access system upon the expiration or
        earlier termination of this Lease in accordance with the provisions of
        Paragraph 26(b).

    (g) To decorate the Common Areas of the Project and to make necessary
        repairs, alterations, additions, changes, or improvements, whether
        structural or otherwise, in and about the Project, and for those
        purposes to enter upon the Leased Premises and, during the continuance
        of the work, temporarily close doors, entryways, public space, and
        corridors in the Project, to interrupt or temporarily suspend Project
        services and facilities, and to change the arrangement and location of
        entrances or passageways, doors and doorways, corridors, elevators,
        stairs, toilets, or other public parts of the Project, all without
        abatement or setoff of Rent or affecting any of Tenant's obligations
        under this Lease, so long as the Leased Premises are reasonably
        accessible and provided that Landlord may make alterations, additions,
        changes, or improvements to the Leased Premises under this Paragraph
        20(g) only to the extent necessary under Applicable Laws or in
        connection with the operation of the Building. Landlord shall use
        commercially reasonable efforts to exercise its rights under this
        Paragraph 20(g) in a way that minimizes interference with Tenant's
        operations in and access to the Leased Premises or access to the parking
        garage at the Project except in emergencies.

                                                                         Page 27
<PAGE>

    (h) To have and retain a paramount title to the Leased Premises and the
        Project free and clear of any act of Tenant purporting to burden or
        encumber the Leased Premises or the Project.

    (i) To grant to anyone the exclusive right to conduct any business or render
        any service in or to the Project if the exclusive right does not operate
        to exclude Tenant from the uses expressly permitted in this Lease.

    (j) To approve the weight, size, and location of safes, heavy equipment,
        file cabinets, book shelves, and other heavy items in and about the
        Leased Premises and the Project and to require all those items and all
        furniture to be moved into and out of the Project and the Leased
        Premises only at reasonable times and in a manner reasonably specified
        by Landlord. Movements of Tenant's property into or out of the Project
        and within the Project are entirely at the risk and responsibility of
        Tenant.

    (k) To take reasonable measures as Landlord deems advisable for the security
        of the Project and its occupants including, without limitation, the
        search of all persons entering or leaving the Project, the evacuation of
        the Project for cause, suspected cause, or for drill purposes, the
        temporary denial of access to the Project, and the closing of the
        Project after Building Standard Hours, subject to Tenant's right to
        admittance when the Project is closed after Building Standard Hours
        under reasonable regulations Landlord may prescribe from time to time.

    (l) To transfer, assign, or convey, in whole or in part, the Project and
        Landlord's rights under this Lease. If Landlord transfers, assigns, or
        conveys its rights under this Lease, Landlord is released from any
        further obligations under this Lease accruing after the date of the
        transfer and Tenant shall look solely to the successor in interest of
        Landlord for performance of the obligations of "Landlord" under this
        Lease.

21. Fire or Other Casualty.
    ----------------------

    (a) If the Leased Premises or any part thereof are damaged by fire or other
        casualty, Tenant shall give prompt notice thereof to Landlord. If the
        Project or either of the Buildings is so damaged by fire or other
        casualty that substantial alteration or reconstruction of the Project or
        any Building is, in Landlord's sole opinion, required (whether or not
        the Leased Premises are damaged) or if any mortgagee under a mortgage or
        deed of trust covering the Project requires that the insurance proceeds
        payable as a result of the fire or other casualty be used to retire the
        mortgage debt, Landlord may, at its sole option, terminate this Lease by
        giving Tenant notice of termination within 60 days after the date of the
        damage. If Landlord does not terminate this Lease under this Paragraph
        21(a), Landlord shall deliver to Tenant a non-binding estimate of the
        time needed to repair and restore the Project within 60 days after the
        date of the damage. If Landlord's estimate states that repair and
        restoration will not be completed within 270 days after the date of the
        damage, Tenant may terminate this Lease by giving Landlord notice of
        termination within 10 business days after the date Tenant receives
        Landlord's estimate. If Landlord or Tenant terminates this Lease under
        this Paragraph 27(a), the Rent abates as of the date of the damage.

                                                                         Page 28
<PAGE>

    (b) If this Lease is not terminated under Paragraph 21(a), Landlord shall
        within 75 days after the date of the damage commence to repair and
        restore the Project (except that Landlord is not responsible for delays
        outside its control) to substantially the same condition in which it was
        immediately prior to the casualty. If Landlord commences restoration of
        the damage, Tenant shall assign to Landlord (or Landlord's designee) all
        net insurance proceeds payable to Tenant under the property insurance
        required under Paragraph 18 related to the Tenant Improvements and other
        improvements in the Leased Premises made by or on behalf of Tenant, and
        Landlord shall repair and replace the Standard Improvements, Tenant
        Improvements, and other improvements in the Leased Premises made by or
        on behalf of Tenant; except that if the cost of the repair and
        replacements for the Tenant Improvements and other improvements in the
        Leased Premises made by or on behalf of Tenant (based on Landlord's or
        its contractor's estimate of the cost) exceeds the insurance proceeds
        received by Landlord from Tenant's insurance carrier (which Tenant shall
        cause its insurance carrier to pay to Landlord), Tenant shall pay the
        shortfall to Landlord prior to Landlord's repair of the damage. No
        Landlord Party is liable for any inconvenience or annoyance to any
        Tenant Party or injury to the business of Tenant resulting in any way
        from casualty damage or the repairs (including any inconvenience,
        annoyance, or injury resulting solely or in part from negligence or
        strict liability, but not gross negligence, of any Landlord Party);
        except that during the time and to the extent the Leased Premises are
        unfit for occupancy, Landlord shall either furnish Tenant with
        comparable office space (including voice and data cabling and controlled
        access system) in the Project at the same Rent as payable under this
        Lease at Landlord's cost or a fair diminution of Rent, the choice of
        which is at Landlord's sole discretion.

    (c) If Landlord commences the restoration or repair and the restoration or
        repair of the Standard Improvements or the Tenant Improvements located
        in the Leased Premises is not completed to the extent necessary so that
        Tenant can occupy the Leased Premises for normal business purposes
        within 270 days after the date of the damage (or any longer time period
        specified in Landlord's estimate under Paragraph 21(a)), then Tenant
        shall have the right, exercisable by notice to Landlord delivered no
        later than 15 business days after the last day of the 270-day period (or
        any longer time period specified in Landlord's estimate under Paragraph
        21(a)), to terminate this Lease as to the untenantable portion of the
        Leased Premises or as to all of the Leased Premises if the untenantable
        portion of the Leased Premises is more than 50% of the Rentable Area of
        the Leased Premises by giving notice of termination to Landlord. If
        Tenant fails to give notice in the manner and within the time period
        specified in the preceding sentence or prior to completion, Tenant's
        option to terminate is deemed irrevocably waived by Tenant.

    (d) Subject to Paragraph 24, if the damages are caused by the negligence or
        willful misconduct of any Tenant Party, Rent abates only to the extent
        of the amount of proceeds of Landlord's business interruption insurance
        received by Landlord related to the Leased Premises and Tenant shall pay
        to Landlord as additional Rent any damages to the Project in excess of
        the amount paid by insurance proceeds received by Landlord.

                                                                         Page 29
<PAGE>

22. Condemnation.
    ------------

    (a) If all or substantially all of the Project or any Building is taken for
        any public or quasi-public use under any governmental law, ordinance, or
        regulation or by right of eminent domain or is sold to the condemning
        authority in lieu of condemnation, then this Lease terminates as of the
        date when physical possession of the portion of the Building or Project
        is taken by the condemning authority. If less than all or substantially
        all of the Project or any Building is taken or sold, Landlord (whether
        or not the Leased Premises are affected) may terminate this Lease by
        giving notice to Tenant within 60 days after the right of election
        accrues, in which event this Lease terminates as of the date when
        physical possession of the portion of the Building and Project is taken
        by the condemning authority.

    (b) If this Lease is not terminated upon any taking or sale of less than all
        or substantially all of the Project:

        (1)  the Rent reduces by an amount representing that part of the Rent
             properly allocable to the portion of the Leased Premises taken or
             sold; and

        (2)  Landlord shall, at Landlord's sole expense, restore the remaining
             portions of the Project to substantially its former condition to
             the extent reasonably deemed feasible by Landlord, but:

             (A)  Landlord's restoration obligation does not exceed the scope of
                  the work done by Landlord in originally constructing the
                  Project and installing Standard Improvements in the Leased
                  Premises;

             (B)  Landlord is not required to spend for the work an amount in
                  excess of the amount received by Landlord as compensation or
                  damages (over and above amounts going to the mortgagee of the
                  property taken) for the part of the Project so taken; and

             (C)  If Landlord does not complete the work within 270 days after
                  the condemnation and Tenant is unable to conduct its business
                  in the Leased Premises in a manner reasonably comparable to
                  that conducted immediately prior to the condemnation, then
                  Tenant may terminate this Lease by delivering notice of
                  termination to Landlord no later than 15 business days after
                  the last day of the 270-day period.

    (c) Landlord is entitled to receive all of the compensation awarded upon a
        taking of any part or all of the Project, including any award for the
        value of the unexpired Lease Term. Tenant is not entitled to and
        expressly waives all claim to any compensation; except that Tenant is
        entitled to receive any award for damages to the Tenant Improvements or
        any personal property and for moving costs, if Tenant's award does not
        reduce the amount of Landlord's award.

                                                                         Page 30
<PAGE>

23. Taxes on Tenant's Property.
    --------------------------

    Tenant shall pay, and shall indemnify, defend, and hold Landlord harmless
    against, all taxes levied or assessed against personal property, furniture,
    fixtures, or Tenant Improvements, and other alterations placed by or for
    Tenant in the Leased Premises. If any taxes for which Tenant is liable are
    levied or assessed against Landlord or Landlord's property and if Landlord
    is required to pay the taxes or if the assessed value of Landlord's property
    is increased by inclusion of personal property, furniture, fixtures, Tenant
    Improvements and other alterations placed by or for Tenant in the Leased
    Premises and Landlord elects to pay the increased taxes, Tenant shall pay to
    Landlord as additional Rent that part of the taxes for which Tenant is
    liable under this Paragraph.

24. Waiver of Subrogation.
    ---------------------

    Each party waives all claims that arise or may arise in its favor against
    the other party, or anyone claiming through or under them, by way of
    subrogation or otherwise, during the Lease Term or any extension or renewal
    thereof, for all losses of, or damage to, any of its property (even if the
    loss or damage is caused by the fault or negligence of the other party or
    anyone for whom the other party is responsible), which loss or damage is
    covered or would be covered by valid and collectible Special Form Property
    insurance policies required to be carried under this Lease without regard to
    the amount of any policy but not including any deductible amount. These
    waivers are in addition to, and not in limitation of, any other waiver or
    release in this Lease with respect to any loss or damage to property of the
    parties. Since these mutual waivers preclude the assignment of any claim by
    way of subrogation (or otherwise) to an insurance company (or any other
    person), each party shall immediately give each insurance company issuing to
    it policies of Special Form Property insurance written notice of the terms
    of these mutual waivers, and have the insurance policies properly endorsed,
    if necessary, to prevent the invalidation of the insurance coverages by
    reason of these waivers.

25. Surrender Upon Termination or Expiration; Holdover.
    --------------------------------------------------

    (a) Upon the Expiration Date or any earlier termination of this Lease,
        Tenant shall: (1) surrender to Landlord possession of the Leased
        Premises in good repair and condition, reasonable wear and tear and
        damages or destruction by any casualty or condemnation excepted, and (2)
        deliver to Landlord all keys to the Leased Premises and all parking
        access cards. If Tenant does not immediately surrender possession, to
        the extent permitted by applicable laws, Landlord may enter upon and
        take possession of the Leased Premises and expel or remove Tenant and
        any other person who may be occupying the Leased Premises, or any part
        thereof, without having any civil or criminal liability therefor.

    (b) If Tenant or any of its successors in interest continues to hold any
        part of the Leased Premises after the termination of this Lease, the
        holding over is a tenancy from month-to-month at a monthly rental equal
        to 150% (for the first 30 days of the holdover) or 200% (for all periods
        after the first 30 days of the holdover) of the monthly Minimum Rent
        payable at the time of termination, plus the payment of all other Rent
        payable under this Lease. While Tenant or its successor continues to
        hold the Leased Premises

                                                                         Page 31
<PAGE>

        after the termination of this Lease, the month-to-month tenancy is
        subject to all terms of this Lease; except that all expansion rights,
        first refusal rights, first notice rights, first offer rights, and
        renewal rights automatically terminate.

    (c) No payments of money by Tenant to Landlord after the termination of this
        Lease reinstate, continue, or extend the Lease Term and no extension of
        this Lease after the termination or expiration thereof is valid unless
        it is reduced to writing and signed by Landlord and Tenant. Nothing in
        this Paragraph may be construed to give Tenant the right to hold over
        beyond the Expiration Date or any earlier termination of this Lease or
        preclude Landlord from having the right to dispossess or otherwise
        terminate Tenant's right of possession. Any month-to-month tenancy is
        terminable upon 30 days' notice from Landlord.

26. Removal of Tenant's Property.
    ----------------------------

    (a) All furniture, movable trade fixtures, and equipment installed by or on
        behalf of Tenant remains the property of Tenant and must be removed by
        Tenant at its sole risk and expense at the termination of this Lease.
        Any removal of Tenant's property must be accomplished in a good and
        workmanlike manner so as not to damage the Leased Premises or the
        Project. Tenant shall promptly repair any damage to the Leased Premises
        or the Project caused by any removal. All furniture, movable trade
        fixtures, and equipment installed by Tenant not removed within 15 days
        after termination of the Lease are conclusively presumed to be abandoned
        by Tenant. Landlord may, at its option, take the possession of the
        property (including any special use improvements) and either (1) declare
        it to be the property of Landlord by notice to Tenant or (2) at the sole
        risk and expense of Tenant and without payment of any compensation to
        Tenant, remove it or any part thereof in any manner that Landlord
        chooses and store, sell, or otherwise dispose of it without incurring
        liability to Tenant or any other person. All amounts payable to Landlord
        under this Paragraph plus interest at the Interest Rate from date of
        payment by Landlord until paid by Tenant are due as additional Rent.

    (b) Upon request of Landlord, Tenant shall also remove, at its sole risk and
        expense, any special use improvements installed by or on behalf of
        Landlord or Tenant in connection with the completion of the Tenant
        Finish Work or otherwise. Any such removal of special use improvements
        must be accomplished in a good and workmanlike manner so as not to
        damage the Leased Premises or the Project. Tenant shall, or Landlord
        may, in its sole discretion and at Tenant's sole expense, repair any
        damage to the Leased Premises or the Project caused by any such removal.
        The term special use improvements means all special improvements
        installed specifically for use by Tenant and includes, without
        limitation, telephone and data cables, computer floors and cables,
        cafeteria equipment, telephones and telephone equipment, supplemental
        air conditioning units and related equipment, equipment supplying excess
        electricity to the Leased Premises, and similar items.

                                                                         Page 32
<PAGE>

27. Events of Default.
    -----------------

    The following are events of default (Events of Default) by Tenant under this
    Lease:

    (a) Tenant fails to pay any Rent when due and the failure continues for a
        period of 5 business days after notice from Landlord. Landlord is
        required to give notice under this Paragraph 27(a) only twice in any 12-
        month period. Landlord is not required to give Tenant notice for the
        third and subsequent Rent payment defaults during any 12-month period
        and, for those defaults, an Event of Default occurs if Tenant fails to
        pay any Rent when due and the failure continues for a period of 5
        business days.

    (b) Tenant fails to comply with any of the terms of this Lease, other than
        the payment of Rent, and does not cure the failure within 30 days after
        Landlord delivers notice of the failure to Tenant; except that, if the
        failure cannot reasonably be cured within the 30-day period, then no
        Event of Default occurs if Tenant commences its cure within the 30-day
        period and diligently completes its cure within 30 days after the last
        day of the 30-day period.

    (c) Tenant or Guarantor, if applicable, becomes insolvent, makes a transfer
        in fraud of creditors, commits any act of bankruptcy, makes an
        assignment for the benefit of creditors, or admits in writing its
        inability to pay its debts as they become due.

    (d) Tenant or Guarantor, if applicable, files a petition under any section
        or chapter of the Bankruptcy Code of the United States, as amended, or
        under any similar law or statute of the United States or any state
        thereof, or Tenant or Guarantor is adjudged bankrupt or insolvent in
        proceedings filed against Tenant or Guarantor, or a petition or answer
        proposing the adjudication of Tenant or Guarantor as a bankrupt or its
        reorganization under any present or future federal or state bankruptcy
        or similar law is filed in any court and the petition or answer is not
        discharged or denied within 120 days after filing.

    (e) A receiver or trustee is appointed for all or substantially all of the
        assets of Tenant or Guarantor, if applicable, or of the Leased Premises
        or of any of Tenant's property located therein in any proceeding brought
        by Tenant or Guarantor, or any receiver or trustee is appointed in any
        proceeding brought against Tenant or Guarantor and is not discharged
        within 120 days after appointment or Tenant or Guarantor shall consent
        to or acquiesce in the appointment.

    (f) Tenant or Guarantor, if applicable, if a natural person, dies or becomes
        incapacitated or, if Tenant or Guarantor is not a natural person, Tenant
        or Guarantor is dissolved or ceases to exist.

    (g) Tenant's leasehold estate is taken on execution or other process of law
        in any action against Tenant.

    (h) Tenant does not conduct its business in any substantial portion of the
        Leased Premises for more than 180 days.

                                                                         Page 33
<PAGE>

28. Landlord's Remedies.
    -------------------

    If an Event of Default occurs, Landlord may then or any time thereafter and
    without any further notice or opportunity to cure except as expressly set
    forth in this Paragraph pursue any one or more of the following remedies:

    (a) Terminate this Lease by giving notice to Tenant, in which event Tenant
        shall immediately surrender the Leased Premises to Landlord. If Tenant
        fails to surrender the Leased Premises, Landlord may, to the extent
        permitted by applicable laws and without prejudice to any other remedy
        it has for possession or arrearages in Rent, take possession of the
        Leased Premises and expel or remove Tenant and any other person
        occupying the Leased Premises, or any part thereof, without being liable
        for prosecution or any claim of damages. Tenant shall pay to Landlord as
        additional Rent the amount of all loss and damage Landlord suffers by
        reason of the termination, whether through inability to re-let the
        Leased Premises on satisfactory terms or otherwise. Landlord has no duty
        to re-let the Leased Premises, except as required by applicable laws.
        Landlord's damages specifically include, but are not limited to: (1) all
        reasonable expenses necessary to recover possession of the Leased
        Premises and re-let the Leased Premises including the cost of
        renovating, repairing, and altering the Leased Premises for a new tenant
        or tenants, advertisements, and brokerage fees; and (2) any increase in
        insurance premiums caused by the vacancy of the Leased Premises.
        Landlord's damages also include an amount equal to (i) the positive sum,
        if any, of the present value of the Rent under this Lease [discounted at
        the prime rate announced as such in the Money Rates section of the Wall
        Street Journal (or alternate source reasonably selected by Landlord)
        issued on the first business day after the date of termination (the
        Discount Rate)] reduced by the present value of the fair market rent
        (based on an assumed lease term equal to the then current Lease Term and
        based on an "AS IS" lease) for the Leased Premises for the Leased
        Premises for the balance of the Lease Term (discounted at the Discount
        Rate) plus (ii) the unamortized (on a straight line basis without
        interest) portion of all leasing commissions and legal fees paid by
        Landlord in connection with the negotiation and execution of this Lease.
        Nothing in this Lease limits Landlord's right to prove and obtain in
        bankruptcy or insolvency proceedings damages by reason of the
        termination of this Lease in an amount equal to the maximum amount
        allowed by any statute or rule of law in effect at the time when the
        damages are to be proved, whether or not the amount is greater, equal
        to, or less than the amount of the loss or damages referred to above.

    (b) Terminate Tenant's right of possession under this Lease without
        terminating this Lease and take possession of the Leased Premises and
        remove Tenant or any other person occupying the Leased Premises, or any
        part thereof, without having any civil or criminal liability and without
        terminating this Lease. Landlord may (but is under no obligation, except
        as required by applicable laws, to) relet the Leased Premises or any
        part thereof for the account of Tenant, in the name of Tenant or
        Landlord or otherwise, without notice to Tenant for a term or terms
        (which may be greater or less than the period that would otherwise have
        constituted the balance of the Lease Term) and on conditions (which may
        include concessions or free rent) and for uses as Landlord in its sole
        discretion may determine. Landlord may collect and receive any rents
        payable by reason of any re-letting. Tenant shall pay Landlord as
        additional Rent all reasonable expenses necessary

                                                                         Page 34
<PAGE>

        to recover possession of the Leased Premises and re-let the Leased
        Premises, which includes the cost of renovating, repairing, and altering
        the Leased Premises for a new tenant or tenants, advertisements, and
        brokerage fees, as well as any deficiency that may arise by reason of
        the re-letting. Except as provided under applicable laws, Landlord is
        not liable for any failure to re-let the Leased Premises or any part
        thereof or for any failure to collect any Rent due upon any re-letting.
        No taking of possession of the Leased Premises by Landlord is an
        election on Landlord's part to terminate this Lease unless a notice of
        termination is given to Tenant.

    (c) Enter upon the Leased Premises without having any civil or criminal
        liability and do whatever Tenant is obligated to do under the terms of
        this Lease. Tenant shall reimburse Landlord as additional Rent for any
        expenses Landlord incurs in performing Tenant's obligations under this
        Lease, together with interest at the Interest Rate from the date
        incurred until repaid by Tenant. Landlord is not liable for any damages
        resulting to Tenant from any Landlord Party's actions or omissions in
        performing Tenant's obligations, whether caused by the negligence or
        strict liability, but not gross negligence, of any Landlord Party or
        otherwise.

    (d) If an Event of Default related to payment of Rent has occurred, Landlord
        may interrupt or cause the interruption of any utility service serving
        the Leased Premises, deactivate Tenant's parking access cards and
        building access cards or keys, suspend elevator service to the Leased
        Premises, remove, alter, or change any door, window, or attic hatchway
        cover to the Leased Premises, or any lock, latch, hinge, hinge pin,
        doorknob, or other mechanism connected to any door, window, or attic
        hatchway cover to the Leased Premises, and intentionally prevent Tenant
        from entering the Leased Premises without resort to judicial process.
        Landlord is under no obligation to restore any door, window, or attic
        hatchway cover or any lock, latch, hinge, hinge pin, doorknob, or other
        mechanism attached thereto or to deliver or make available to Tenant any
        key to any door, window, or attic hatchway cover until Tenant fully
        cures all Events of Default related to payment of Rent then existing
        under this Lease.

    No repossession of or re-entering all or any part of the Leased Premises
    under subparagraphs 28(b), (c), or (d) above or otherwise and no re-letting
    of the Leased Premises or any part thereof under subparagraph 28(b) relieves
    Tenant or Guarantor of any liabilities or obligations under this Lease, all
    of which survive repossession or re-entering by Landlord. If Landlord
    repossesses or re-enters all or any part of the Leased Premises after an
    Event of Default, Tenant shall pay to Landlord the Rent required to be paid
    by Tenant. No right or remedy of Landlord under this Lease is intended to be
    exclusive of any other right or remedy. Each right and remedy of Landlord is
    cumulative of all other rights or remedies under this Lease or now or
    hereafter existing at law, in equity or by statute. In addition to other
    remedies provided in this Lease, Landlord is entitled, to the extent
    permitted by Applicable Laws, to injunctive relief in case of the violation,
    or attempted or threatened violation, of any of the terms of this Lease, or
    to a decree compelling specific performance of the terms of this Lease.

                                                                         Page 35
<PAGE>

    If Landlord is deemed to have a duty to mitigate its damages arising from a
    default by Tenant under this Lease, then Landlord's duty to mitigate is
    limited to using objectively reasonable efforts to relet the Leased Premises
    to a replacement tenant suitable under the circumstances, which duty to
    relet the Leased Premises does not require Landlord to (i) give priority to
    the Leased Premises over other premises owned or managed by Landlord or its
    affiliates, (ii) relet for less than market rent, or (iii) relet to a tenant
    (or for a use) that is not in keeping with the first class character of the
    Project. Further, any breach of Landlord's duty to relet the Leased Premises
    does not give rise to a cause of action by Tenant, but rather, will reduce
    Landlord's recovery against Tenant to the extent that damages reasonably
    could have been avoided if Landlord had properly exercised its above-
    described duty.

    Notwithstanding anything to the contrary in this Lease, Tenant shall not be
    liable for payment to Landlord for any special or consequential damages as a
    result of any Event of Default by Tenant.

29. No Implied Waiver.
    -----------------

    The failure of Landlord or Tenant to insist at any time upon the strict
    performance of any of the terms of this Lease or to exercise any option,
    right, power, or remedy contained in this Lease is not a waiver of the right
    or remedy for the future. The waiver of any breach of this Lease or
    violation of the Rules and Regulations attached to this Lease does not
    prevent a subsequent act, which would have originally constituted a breach
    or violation, from having all the force and effect of an original breach or
    violation. No express waiver affects any terms other than the ones specified
    in the waiver and those only for the time and in the manner specifically
    stated. Acceptance by Landlord of any Rent after the breach of any of the
    terms of this Lease or violation of any Rule or Regulation is not a waiver
    of the breach or violation or the right to collect applicable late charges
    and interest. Payment by Tenant of any Rent after any default by Landlord
    under this Lease is not a waiver by Tenant of Landlord's default or any
    remedies available to Tenant under this Lease for Landlord's default. No
    waiver by Landlord or Tenant of any of the terms of this Lease is effective
    unless expressed in writing and signed by the party to be bound by the
    waiver.

30. Waiver by Tenant.
    ----------------

    Tenant waives and surrenders for itself and all persons or entities claiming
    by, through, and under it, including creditors of all kinds: (A) any right
    and privilege which it or any of them has under any present or future
    constitution, statute, or rule of law to redeem the Leased Premises or to
    have a continuance of this Lease for the Lease Term after termination of
    Tenant's right of occupancy by order or judgment of any court or by any
    legal process or writ, or under the terms of this Lease; (B) the benefits of
    any present or future constitution, statute, or rule of law that exempts
    property from liability for debt or for distress for Rent; (C) any provision
    of law relating to notice or delay in levy of execution in case of eviction
    of a tenant for nonpayment of Rent; (D) any rights, privileges, and liens
    set out under Sections 91.004 and 93.003 of the Texas Property Code (as
    amended), and Tenant exempts Landlord from any liability or duty thereunder,
    and (E) any rights of Tenant to contest reappraisals of the Project (but not
    ad valorem taxes on Tenant's personal property in the Leased Premises) under
    Sections 41.413 and 42.015 of the Texas Tax Code (as amended).

                                                                         Page 36
<PAGE>

31. Legal Expenses.
    --------------

    If either party files litigation concerning the interpretation or
    enforcement of this Lease, the prevailing party is entitled to recover from
    the losing party the prevailing party's reasonable legal fees, court costs,
    and expenses, whether at the trial or appellate level.

32. Subordination.
    -------------

    (a) This Lease and all rights of Tenant under this Lease are subject and
        subordinate to:

        (1) any mortgage or deed of trust secured by a first lien against the
            Project only if Landlord causes the holder of the first lien to join
            with Tenant in the execution and delivery of a Subordination,
            Nondisturbance, and Attornment Agreement in substantially the form
            attached to this Lease as Exhibit K and to all increases, renewals,
                                      ---------
            modifications, consolidations, replacements, and extensions of the
            first lien mortgage or deed of trust; and

        (2) all restrictions, easements, and encumbrances recorded in the Real
            Property Records of Dallas County, Texas, as of the Commencement
            Date, to the extent they validly affect the Project. Tenant shall,
            upon demand at any time or times, execute, acknowledge, and deliver
            to Landlord, or to Landlord's first mortgagee, any instruments that
            may be necessary or proper to more effectively effect or evidence
            this subordination to any first mortgage or first deed of trust;
            provided the instruments do not modify the terms of this Lease.

    (b) Landlord represents and warrants to Tenant that there is no first
        mortgage or first deed of trust against the Project or any ground lease
        affecting any portion of the Project.

33. Quiet Enjoyment.
    ---------------

    If Tenant pays the Rent when due and timely performs all other obligations
    of Tenant under this Lease, then Tenant may peaceably and quietly enjoy the
    Leased Premises during the Lease Term without any disturbance from Landlord
    or from any other person claiming by, through, or under Landlord, but not
    otherwise, subject to the terms of this Lease and of the deeds of trust,
    mortgages, ordinances, utility easements, and agreements to which this Lease
    is subordinate.

34. Notice of Landlord's Default.
    ----------------------------

    If any act or omission by any Landlord Party occurs that would give Tenant
    the right to damages from Landlord or the right to terminate this Lease due
    to constructive or actual eviction from all or part of the Leased Premises
    or otherwise, Tenant may not sue for damages or exercise any right to
    terminate until (A) it gives notice of the act or omission to Landlord and
    Landlord's first mortgagee, if any, provided Landlord has delivered notice
    of the name and address of the first mortgagee to Tenant and (B) a
    reasonable period of time for remedying the act or omission elapses
    following the giving of the notice, during which time Landlord, its agents,
    employees, and first mortgagee are entitled to enter the Leased Premises and
    cure the act or omission.

                                                                         Page 37
<PAGE>

35. Project Rules and Regulations.
    -----------------------------

    All Tenant Parties must comply with the Project Rules and Regulations (as
    changed from time to time as hereinafter provided) attached as Exhibit C.
                                                                   ---------
    Landlord may at any time change the Project Rules and Regulations or
    promulgate other Project Rules and Regulations as Landlord deems advisable
    for the safety, care, cleanliness, or orderliness of the Project so long as
    no change materially adversely affects the rights or obligations of Tenant
    under this Lease. No changes are effective until a copy of the changes is
    delivered to Tenant. Tenant is responsible for the compliance with the
    Project Rules and Regulations by all Tenant Parties. Landlord shall use
    reasonable efforts to enforce compliance by all other tenants with the
    Project Rules and Regulations from time to time in effect, but Landlord
    Parties are not responsible to Tenant for failure of any person to comply
    with the Project Rules and Regulations. The provisions of this Lease will
    control if there is a conflict with any existing or future Project Rules and
    Regulations.

36. Estoppel Certificate.
    --------------------

    Tenant shall, from time to time on not less than 20 days' prior notice by
    Landlord, execute, acknowledge, and deliver to Landlord an Estoppel
    Certificate in substantially the form attached as Exhibit E, with
                                                      ---------
    appropriate modifications needed to correct any incorrect statements.

37. Notices.
    -------

    All notices, requests, approvals, consents, and other communications
    required or permitted to be delivered under this Lease must be in writing
    and are effective and are deemed delivered:

    (a) on the business day sent if (1) sent by telecopier prior to 5:00 p.m.,
        Dallas, Texas time, (2) the sending telecopier generates a written
        confirmation of sending, and (3) a confirming copy is sent on the same
        business day by one of the other means specified below;

    (b) the next business day after delivery on a business day to a nationally-
        recognized-overnight-courier service for prepaid overnight delivery;

    (c) if orderly delivery of the mail is not then disrupted or threatened, in
        which event some method of delivery other than the mail must be used, 3
        days after being deposited in the United States mail, certified, return
        receipt requested, postage prepaid; or

    (d) upon receipt if delivered personally or by any method other than by
        telecopier (with written confirmation), nationally-recognized-overnight-
        courier service, or mail;

    in each instance addressed to Landlord or Tenant, as the case may be, at the
    address specified in Paragraph 1 of this Lease, or to any other address
    either party may designate by 10 days' prior notice to the other party.

                                                                         Page 38
<PAGE>

    With respect to any default notice to Landlord, a copy of the notice must be
    sent on the same date as sent to Landlord to:

                    Munsch Hardt Kopf & Harr, P.C.
                    4000 Fountain Place
                    1445 Ross Avenue
                    Dallas, Texas 75202-2790
                    Attention: B. Carl Klinke
                    Telecopier No.: (214) 978-4310

    With respect to any notice to Tenant, a copy of the notice must be sent on
    the same date as sent to Tenant to:

                    Thompson & Knight, LLP
                    801 Cherry Street
                    Suite 1600
                    Fort Worth, Texas 76102
                    Attention: Susan E. Coleman
                    Telecopier No.: (817) 347-1799

38. Hazardous Materials.
    -------------------

    (a) Tenant may not:

        (1)  cause or permit the escape, disposal, or release in the Leased
             Premises or the Project of any biologically active, chemically
             active, or hazardous substances or materials (collectively,
             hazardous substances); or

        (2)  bring, or permit any other Tenant Party to bring, any hazardous
             substances into the Leased Premises or the Project other than
             normal cleaning and office supplies stored, used, and disposed of
             in compliance with Applicable Laws.

        The term hazardous substances includes, but is not limited to, those
        described in the Comprehensive Environmental Response Compensation and
        Liability Act of 1980, as amended, 42 U.S.C. Section 9601 et seq., the
        Resource Conservation and Recovery Act, as amended, 42 U.S.C. Section
        6901 et seq., the Texas Water Code, the Texas Solid Waste Disposal Act,
        and other applicable existing and future state or local environmental
        laws and the regulations adopted under those acts, as amended.

    (b) If any lender or governmental agency requires testing to ascertain
        whether or not a release of hazardous substances has occurred in or on
        the Leased Premises or the Project based on probable cause that a
        release occurred and was caused by any Tenant Party (excluding any
        release of any hazardous substances present in the Leased Premises or
        the Project as of the Commencement Date and not brought into the Project
        by any Tenant Party, whether the release was caused by any Tenant Party
        or otherwise, except as specified in Paragraph 38(d)(ii)), then Tenant
        shall reimburse the reasonable costs of the testing to Landlord as
        additional Rent if there is a release that was caused by any Tenant
        Party and was not a release of any hazardous substances present in the

                                                                         Page 39
<PAGE>

        Leased Premises or the Project as of the Commencement Date not brought
        into the Project by any Tenant Party.

    (c) Tenant shall execute affidavits, representations, and the like from time
        to time at Landlord's request concerning Tenant's best knowledge and
        belief regarding the presence of hazardous substances brought into the
        Leased Premises or the Project by any Tenant Party.

    (d) Tenant shall indemnify Landlord Parties in the manner elsewhere provided
        in this Lease from (i) any release in or on the Leased Premises or the
        Project of hazardous substances brought into the Project by any Tenant
        Party caused or permitted by any Tenant Party and (ii) any release of
        asbestos-containing materials labeled "Asbestos-Containing Materials, Do
        Not Disturb" (or substantially similar labeling) present in the Project
        as of the Commencement Date caused by any Tenant Party. Except as
        specified in the prior sentence, Tenant has no liability related to the
        presence, release, or disposal of hazardous substances on or from the
        Project that were present in the Project on the Commencement Date or
        thereafter brought into the Project unless the hazardous substances were
        brought into the Project by any Tenant Party.

    (e) Tenant acknowledges receipt of a copy of a Report of Limited Survey for
        Asbestos-Containing Materials for Xerox Center dated September 1996,
        prepared by Law Engineering & Environmental Services, Inc., in
        connection with its Project No. 60342-6-5635 (the Law Report). Landlord
        makes no, and Tenant waives any, representations or warranties related
        to the completeness or accuracy of the Law Report or the right of Tenant
        to rely on the Law Report. If any asbestos-containing materials present
        in the Project (other than any asbestos-containing materials brought
        into the Project by any Tenant Party or any other tenant in the Project)
        are required to be removed under Applicable Laws, Landlord shall
        promptly cause the removal of the asbestos-containing materials in
        compliance with Applicable Laws.

    (f) These covenants (other than Landlord's obligations under the last
        sentence of Paragraph 38(e)) survive the expiration or earlier
        termination of this Lease.

39. Business Purpose.
    ----------------

    Tenant represents that this Lease is executed by Tenant, and all obligations
    of Tenant arising out of this Lease are, primarily for business or
    commercial purposes and not for personal, family, or household purposes.

40. Severability.
    ------------

    Each of the terms of this Lease is, and must be construed to be, separate
    and independent. If any of the terms of this Lease or its application to any
    person or circumstances is to any extent invalid and unenforceable, the
    remainder of this Lease, or the application of that term to persons or
    circumstances other than those as to which it is invalid or unenforceable,
    are not affected thereby.

                                                                         Page 40
<PAGE>

41. No Merger.
    ---------

    The fact that the same person may acquire or hold, directly or indirectly,
    this Lease or the leasehold estate hereby created or any interest in this
    Lease or in the leasehold estate as well as the fee estate in the Leased
    Premises or any interest in the fee estate does not cause a merger of this
    Lease or of the leasehold estate hereby created with the fee estate in the
    Leased Premises.

42. Force Majeure.
    -------------

    When this Lease prescribes a period of time for action to be taken by either
    party, the responsible party is not liable for, and there is excluded from
    the computation of the period of time, any delays due to strikes, acts of
    God, shortages of labor or materials, war, governmental laws, regulations,
    restrictions, or any other cause of any kind that is beyond the control of
    the party. The prior sentence does not apply to the obligation of Tenant or
    Landlord to pay any sum due under this Lease.

43. Brokerage; Mutual Indemnities.
    -----------------------------

    (a) Tenant warrants that it has had no dealings with any broker or agent in
        connection with the negotiation or execution of this Lease other than
        Tenant's Broker and Landlord's Broker (collectively, Brokers). Tenant
        shall indemnify, defend, and hold Landlord harmless against all costs,
        expenses, legal fees, or other liability for commissions or other
        compensation or charges claimed by any broker or agent other than
        Brokers claiming by, through, or under Tenant with respect to this Lease
        or any renewal or extension or with respect to any expansion of the
        Leased Premises.

    (b) Landlord warrants that it has had no dealings with any broker or agent
        in connection with the negotiation or execution of this Lease other than
        Brokers. Landlord shall indemnify, defend, and hold Tenant harmless
        against all costs, expenses, legal fees, or other liability for
        commissions or other compensation or charges claimed by any broker or
        agent, including Brokers, claiming by, through or under Landlord with
        respect to this Lease or any renewal or extension or with respect to any
        expansion of the Leased Premises.

    (c) Any brokerage commissions payable to Brokers are payable by Landlord
        under the terms of separate agreements between Landlord and Brokers.

44. Gender.
    ------

    Words of any gender used in this Lease include any other gender and words in
    the singular number include the plural, unless the context otherwise
    requires.

                                                                         Page 41
<PAGE>

45. Joint and Several Liability.
    ---------------------------

    If there is more than one Tenant, the obligations imposed upon Tenant under
    this Lease are joint and several. If Tenant is a general or limited
    partnership, each general partner of Tenant is jointly and severally liable
    for the obligations imposed upon Tenant under this Lease.

46. No Representations.
    ------------------

    No Landlord Party made any representations or promises with respect to the
    Leased Premises or the Project except as expressly set forth in this Lease.
    No rights, easements, or licenses are acquired by Tenant by implication or
    otherwise except as expressly set forth in this Lease.

47. Entire Agreement; Amendments.
    ----------------------------

    This Lease is the entire agreement between the parties. All negotiations,
    considerations, representations, understandings, and prior agreements
    (including, without limitation, the Permittee Agreement covering Suites 250E
    and 260E) between Landlord and Tenant are superceded by this Lease. No act
    or omission of any employee or agent of Landlord or of Landlord's Broker may
    alter, change, or modify any of the terms of this Lease. No amendment or
    modification of this Lease is binding unless expressed in a written
    instrument executed by Landlord and Tenant.

48. Paragraph Headings.
    ------------------

    The paragraph headings in this Lease are for convenience only and in no way
    enlarge or limit the scope or meaning of the paragraphs in this Lease.

49. Binding Effect.
    --------------

    All terms of this Lease are binding upon the respective heirs, personal
    representatives, successors, and, to the extent assignment is permitted,
    assigns of Landlord and Tenant.

50. Exhibits.
    --------

    The following exhibits are attached to and made a part of this Lease:

    Exhibit A [Leased Premises], B [Land], C [Project Rules and Regulations], D
    ---------                    -         -                                  -
    [Contractor Insurance Requirements], E [Estoppel Certificate], F [Tenant
                                         -                         -
    Finish Construction,] G [Floor Plan of Suite 450E], H [First Notice Space],
                          -                             -
    I [List of Permitted Temporary Occupants], J [Minimum Rent Schedule], and K
    -                                          -                              -
    [Subordination, Nondisturbance, and Attornment Agreement].

51. Counterparts.
    ------------

    This Lease may be executed in two or more counterparts, each of which is
    deemed an original and all of which together constitute one and the same
    instrument.

                                                                         Page 42
<PAGE>

52. Rental Tax.
    ----------

    Tenant shall pay as additional Rent all licenses, charges, and other fees of
    every kind and nature as and when they become due arising out of or in
    connection with Tenant's use and occupancy of the Leased Premises and the
    Project (including the parking garages), including but not limited to
    license fees, business license taxes, and privilege, sales, excise, or other
    taxes (other than income) imposed upon Rent or upon services provided by
    Landlord or upon Landlord in an amount measured by Rent received by
    Landlord.

53. Parking.
    -------

    (a) During the Lease Term:

        (1)  Landlord shall provide Tenant with parking access cards for
             unreserved parking in a parking garage at the Project specified by
             Landlord at a ratio of 1 parking access card for each 300 RSF in
             the Leased Premises (see Exhibit J), at no charge to Tenant.
                                      ---------

        (2)  By giving notice to Landlord, Tenant may elect to rent additional
             parking access cards (the Additional Cards) for the remainder of
             the initial Lease Term, also for unreserved parking in a parking
             garage at the Project specified by Landlord, to increase the number
             of unreserved parking access cards held by Tenant up to a maximum
             of 1 parking access card for each 250 RSF in the Leased Premises at
             $25 per parking card per month. Upon request by Tenant, Landlord
             will waive the $25 per parking card per month fee for up to 8
             Additional Cards to be used for Tenant employees working Tenant's
             second shift and for up to 8 Additional Cards to be used for Tenant
             employees working Tenant's third shift. Tenant will provide
             Landlord with a list of the names, work phone numbers, and
             automobile license numbers for Tenant employees working the second
             and third shifts and will update the list as necessary to keep it
             current. Tenant acknowledges that Landlord will restrict the use of
             the parking access cards so that they will provide access to the
             parking garage only during time periods 1 hour on each side of
             Tenant's second or third shift, as applicable. If Landlord
             determines that these restricted parking cards are being used
             (including attempted use at the wrong times) at times other than
             Tenant's second or third shift, as applicable, Tenant shall pay
             rent at the rate specified above for the parking access cards that
             were used at the wrong time commencing on the date Landlord
             notifies Tenant of the incorrect usage.

        (3)  Tenant may elect to convert up to 10 free unreserved parking access
             cards to reserved parking access cards for the remainder of the
             initial Lease Term, in a parking garage at the Project and at
             locations specified by Landlord, at $50 per parking card per month.
             Landlord may relocate reserved parking spaces within the Project at
             any time, at Landlord's reasonable discretion, upon 5 days prior
             written notice to Tenant, but the reserved parking spaces must be
             for covered parking spaces.

                                                                         Page 43
<PAGE>

    (b) Prior to each issuance of parking access cards, Tenant must deliver to
        Landlord a list of the automobile license numbers of Tenant's employees
        who will be using the cards. If any card is lost or damaged or not
        returned to Landlord on request, and Landlord's then current per card
        deposit must be delivered to Landlord before a replacement card is
        issued to Tenant.

    (c) The provisions of Paragraphs 53(a) and 53(b) do not apply to Suite 450E.
        The number of parking access cards to be made available to Tenant in
        connection with the addition of Suite 450E to the Leased Premises is
        governed by Paragraph 55(e).

    (d) With regard to unreserved parking, Tenant is not assigned designated
        parking spaces, but is permitted to use whatever unreserved stalls are
        available, on a first-come, first-served basis in areas of the parking
        garage designated from time to time by Landlord. If for any reason
        parking spaces in the parking garage are not available for use by Tenant
        Parties, this failure or inability is not a default by Landlord under
        this Lease.

    (e) All Tenant Parties must comply with all traffic, security, safety, and
        other rules and regulations promulgated from time to time by the
        operator of the garage.

    (f) During any renewal or extension of the Lease Term or during any holdover
        after the termination of this Lease, Landlord reserves the right to
        charge Tenant the then market rate for parking access cards at the
        Project unless Landlord agrees otherwise at the time of the renewal or
        extension.

    (g) If Landlord exercises its termination right set forth in subparagraph
        11(f)(1) above, the number of parking access cards allocated to Tenant
        reduces proportionately, effective as of the date of termination.

    (h) With respect to unreserved parking, Tenant is not assigned designated
        parking spaces but is permitted to use whatever unreserved stalls are
        available, on a first-come, first-served basis in areas of the parking
        garage designated from time to time by Landlord. If for any reason
        parking spaces in the parking garage are consistently not available for
        use by Tenant Parties, this failure or inability is not a default by
        Landlord under this Lease. If 25% or more of Tenant's employees
        attempting to use parking access cards on a first-come, first-served
        basis are unable to find parking spaces in the parking garage for 5
        consecutive business days, then Tenant shall give Landlord a detailed
        notice specifying the applicable facts. Within 20 days after receipt of
        Tenant's notice, Landlord shall retain an independent consultant, at
        Tenant's cost and expense to be paid to Landlord in advance, to
        determine, within 45 days after Landlord retains the consultant, whether
        the Project is overparked. The term overparked means that the number of
        parking spaces available at or to the Project persistently does not
        provide adequate parking on a first-come, first-served basis to permit
        Tenant the use of the number of parking access cards provided to Tenant
        under this Lease.

        If the consultant determines that the Project is overparked, then (i)
        Landlord shall reimburse Tenant for the costs charged by the consultant
        for the study and Landlord shall make commercially reasonable efforts to
        locate and provide suitable additional or alternative parking to Tenant
        for the number of spaces displaced within 60 days after the

                                                                         Page 44
<PAGE>

        consultant's findings are detailed, and (ii) parking card rent will be
        proportionately abated based on the number of Tenant's employees using
        parking access cards unable to find parking spaces on a first-come,
        first-served basis during the period commencing with the date Landlord
        received Tenant's detailed notice and continuing until additional
        parking spaces become available. If on 2 occasions during the Lease Term
        a consultant retained under this Paragraph 53(h) determines that the
        Project is not overparked, then Tenant has no further rights under this
        Paragraph 53(h).

        In addition, if the number of parking spaces at the Project is reduced
        by 25% or more due to condemnation or other reduction by Landlord, other
        than temporary reductions in connection with repairs, restorations, and
        alterations (including repairs, restorations, and alterations related to
        casualty damage and condemnation), Landlord shall make commercially
        reasonable efforts to locate and provide suitable additional or
        alternative parking to Tenant for the number of spaces displaced within
        120 days after the date of the reduction. Landlord shall not voluntarily
        reduce, other than temporary reductions in connection with repairs,
        restorations, and alterations (including repairs, restorations, and
        alterations related to casualty damage and condemnation), the number of
        parking spaces available at the Project on the Commencement Date by more
        than 10%. A reduction in parking spaces due to a transfer by Landlord in
        lieu of condemnation is not a voluntary reduction for the purposes of
        the prior sentence. The term "alterations" as used in this Paragraph
        53(h) includes the construction of additional parking decks on the
        parking garage at the Project, which construction is at Landlord's sole
        discretion. The inclusion of the prior sentence in this Paragraph 53(h)
        may not be used to infer that the construction of additional parking
        decks on the parking garage at the Project is a commercially reasonable
        method for Landlord to provide additional parking at the Project.

54. Tenant's Service Providers.
    --------------------------

    Tenant shall cause all moving companies and other entities providing
    services to Tenant to deliver evidence reasonably satisfactory to Landlord
    that the insurance specified in Exhibit D is in force prior to entering the
                                    ---------
    Project.

55. Option to Expand the Leased Premises.
    ------------------------------------

    (a) If Tenant is not in default under this Lease at the time of the exercise
        of this option or at the time of the Suite 450E Commencement Date
        (defined below), Tenant shall have the option, exercisable by giving
        notice to Landlord (the Expansion Notice) no later than March 31, 2001,
        and subject to the following provisions, to lease from Landlord Suite
        450E, located in the East Tower and consisting of approximately 22,663
        Rentable Square Feet as shown on Exhibit G attached hereto.
                                         ---------

    (b) If Tenant timely and properly gives the expansion Notice, then Suite
        450E will be added to the Leased Premises effective as of November 1,
        2001 (the Suite 450E Commencement Date) and the Leased Premises will
        thereafter consist of approximately 91,428 Rentable Square Feet and
        Tenant's pro rata share of Total Electricity Costs will increase to
        10.95%.

                                                                         Page 45
<PAGE>

    (c) Tenant must pay to Landlord along with the Expansion Notice, an amount
        equal to the last month's Minimum Rent payment for Suite 450E [as
        determined under Paragraph 55(d)], as an increase to the Security
        Deposit under this Lease.

    (d) Effective on the Suite 450E Commencement Date, the Minimum Rent for
        Suite 450E is, and the Minimum Rent under this Lease increases, as
        follows: (i) if Tenant delivers the Expansion Notice on or before August
        31, 2000, then the Minimum Rent increases by $43,437.42 per month from
        11-1-2001 through 5-31-2002, and by $44,381.71 from 6-1-2002 through the
        Expiration Date; or (ii) if Tenant delivers the Expansion Notice after
        August 31, 2000, then the Minimum Rent increases by $45,326.00 per month
        from 11-1-2001 through the remainder of the initial Lease Term.

    (e) Beginning on the Suite 450E Commencement Date, Landlord shall provide to
        Tenant an additional 81 parking access cards for unreserved parking in a
        parking garage at the Project specified by Landlord, at no charge to
        Tenant. During the initial Lease Term and after the Suite 450E
        Commencement Date, Tenant may elect, exercisable by at least 30 days'
        notice to Landlord and subject to availability as determined by Landlord
        in its sole discretion, to rent an additional 20 parking access cards
        for the remainder of the initial Lease Term, also for unreserved parking
        in a parking garage at the Project specified by Landlord, at $25 per
        parking card per month.

    (f) Tenant and Landlord acknowledge that Tenant currently occupies and uses
        Suite 450E under that certain Sublease dated June 28, 1999 (the
        Sublease) by and between Tenant, as Subtenant, and Eastman Kodak
        Company, a New Jersey corporation (Eastman), as Sublandlord, which
        Sublease expires by its own terms on October 31, 2001. Tenant and
        Landlord also acknowledge that Eastman has waived any renewal rights it
        had as to Suite 450E under that certain Office Lease dated September 16,
        1996, by and between HMS Office, L.P., as predecessor in interest to
        Landlord, and Eastman.

    (g) Suite 450E will be leased to and accepted by Tenant in its "AS-IS"
        condition. Tenant agrees that, except as provided in this Lease,
        Landlord has no obligation to improve, repair, restore, or refurbish
        Suite 450E. Tenant's continued occupancy of Suite 450E or any portion
        thereof is conclusive evidence that Tenant (i) accepts Suite 450E as
        suitable for the purposes for which it is leased; (ii) accepts Suite
        450E as being in a good and satisfactory condition; (iii) waives any
        defects in Suite 450E; and (iv) agrees that the Rentable Square Feet
        numbers specified in this Paragraph 55 are binding and conclusive for
        all purposes under this Lease.

    (h) If Suite 450E is added to the Leased Premises under this Paragraph 55,
        Landlord shall prepare, and Landlord and Tenant shall execute and
        deliver, an appropriate amendment to the Lease to reflect the terms of
        the Extended Lease Term.

56. Option to Extend Lease Term for the Original Leased Premises.
    ------------------------------------------------------------

    (a) If Tenant is not in default under this Lease at the time of the exercise
        of this option or at the commencement of the Extended Lease Term
        (defined below), Tenant may extend the initial Lease Term as to Suites
        250E, 260E, 350E, 300N, 450E (if Tenant has exercised the expansion
        option set forth in Paragraph 55), and 400N only (collectively,

                                                                         Page 46
<PAGE>

        the Original Leased Premises), for 1 extension term of 5 years
        commencing on the next day after the initial Expiration Date by giving
        Landlord an extension notice at least 8 months, but not more than 15
        months, prior to the initial Expiration Date (the Extension Notice
        Period). If Tenant gives a valid extension notice during the Extension
        Notice Period, then, unless Tenant gives a timely revocation notice
        under Paragraph 56(b), the Lease Term as to the Original Leased Premises
        only is extended for 5 years (the Lease Term as extended herein is
        called the Extended Lease Term) upon the same terms as in this Lease,
        except that the Rent, parking charges, and other applicable terms for
        the Original Leased Premises only adjust based on the Market Rate
        (defined below) and Tenant has no further option to extend the Extended
        Lease Term after this option is exercised. If Tenant does not give an
        extension notice during the Extension Notice Period, then this option
        expires automatically on the next day after the last day of the
        Extension Notice Period. Landlord is not required to give Tenant notice
        of the beginning or end of the Extension Notice Period.

    (b) Within 30 days after Landlord receives Tenant's extension notice,
        Landlord shall deliver a notice to Tenant specifying the Market Rate. If
        Tenant does not approve Landlord's designation of Market Rate, then
        Landlord and Tenant shall negotiate in good faith for a period of 30
        days after the date of Landlord's notice to reach agreement on the
        Market Rent. If Landlord and Tenant do not reach agreement on the Market
        Rent within the 30-day period, then Tenant, as its sole remedy, may
        revoke its exercise notice by delivering a revocation notice to Landlord
        within 15 days after the last day of the 30-day negotiation period, but
        otherwise Tenant may not revoke its extension notice. If Tenant timely
        gives a revocation notice, then the Lease Term as to the Original Leased
        Premises only ends on the initial Expiration Date and Tenant has no
        further rights under this Paragraph 56. If Landlord and Tenant do not
        reach agreement on the Market Rent within the 30-day period and Tenant
        does not timely give a revocation notice, Tenant is deemed to approve
        the Market Rate specified in Landlord's notice.

    (c) The term Market Rate means the minimum rent determined by Landlord,
        taking into consideration all relevant factors, including, without
        limitation, the following: lease term; commencement date; work
        allowance; Base Year; parking rates; after-hours HVAC charges; rent
        being charged in comparable office buildings located in the Las Colinas
        Urban Center for leases then being entered into for comparable space to
        the Original Leased Premises; location, quality, amenities, age, and
        reputation of the buildings in which the space being compared is
        located; use and size of the space under comparison; location and floor
        level of the subject space and any comparison space within their
        respective buildings, including elevator lobby exposure; except that the
        Rent components of the Market Rate will not be less than the average
        Rent being paid under this Lease for the Original Leased Premises only
        at the end of the Lease Term.

    (d) If the Lease Term is extended under this Paragraph 56, Landlord shall
        prepare, and Landlord and Tenant shall execute and deliver, an
        appropriate amendment to the Lease to reflect the agreed terms of the
        Extended Lease Term.

                                                                         Page 47
<PAGE>

57. Security Disclaimer.
    -------------------

    Any security measures provided by Landlord are not a guarantee against
    crime. Landlord does not make, and Tenant waives, any guaranty or warranty,
    expressed or implied, with respect to security at the Project or in the
    Buildings, or that any security measures will prevent occurrences or
    consequences of criminal activity. Any mechanical security devices can be
    rendered inoperative at any time. Landlord Parties are not responsible for a
    temporary failure of the devices. If any mechanical security devices are in
    need of repair, then Tenant waives all warranties, expressed or implied,
    with respect to Landlord's repair of the devices. Landlord's installation or
    use of any security measure does not constitute a voluntary undertaking or
    agreement by Landlord to provide security to any Tenant Party. Landlord may
    modify, reduce or eliminate the use of any security measure at any time
    without notice to Tenant. Neither Landlord nor any Landlord Parties are
    liable in any way for any disruption in the operation or performance of any
    security measure. Landlord does not make, and Tenant waives, any guaranty or
    warranty that the presence of any security measure at the Project or in the
    Buildings in any way increases the personal security of any Tenant Party or
    its property. Landlord Parties are not liable to any Tenant Party for any
    injury, damage, or loss whatsoever caused (A) as a result of any problem,
    defect, malfunction or the failure of the performance of any security
    measure or (B) by any person engaging in criminal activity.

58. Landlord's Consents and Approvals..
    ---------------------------------

    Whenever Landlord is required to give its reasonable consent or reasonable
    approval under this Lease, Landlord may not unreasonably withhold or delay
    its consent or approval.

59. Intentionally Deleted.
    ---------------------

60. Right of First Notice.
    ---------------------

    (a) If during the Lease Term Landlord proposes to lease the space consisting
        of approximately 21,121 Rentable Square Feet located on the 5th floor of
        the North Tower as shown on Exhibit H attached to this Lease (the First
                                    ---------
        Notice Space) to a third party prospect, then Landlord shall deliver a
        notice to Tenant offering to lease the First Notice Space to Tenant.
        Landlord's notice must specify the First Notice Rate (defined below) and
        the lease term (the First Notice Space Lease Term) for the First Notice
        Space that Landlord proposed to the third party prospect.

    (b) Tenant must respond to Landlord's notice by delivering a notice (the
        Response Notice) to Landlord within 5 business days after the date of
        Landlord's notice specifying that Tenant elects either (i) to lease all,
        but not less than all, of the First Notice Space or (ii) to decline to
        lease the First Notice Space.

    (c) If (i) Landlord does not receive the Response Notice within the 5
        business day period or (ii) in the Response Notice Tenant does not elect
        to lease all of the First Notice Space, then Tenant is deemed to waive
        its right to lease the First Notice Space and Tenant has no further
        rights under this Paragraph 60.

                                                                         Page 48
<PAGE>

    (d) If Tenant timely delivers a Response Notice electing to lease all of the
        First Notice Space, then the First Notice Space will be added to the
        Leased Premises on the date Landlord delivers possession of the First
        Notice Space to Tenant and Tenant's obligation to pay Rent for the First
        Notice Space will commence on the 61st day after the date Landlord
        delivers possession of the First Notice Space to Tenant. The First
        Notice Space will be added to the Leased Premises on the same terms as
        this Lease except that (i) the Lease Term for the applicable First
        Notice Space will be the First Notice Space Lease Term specified in
        Landlord's notice for the First Notice Space, and (ii) Rent and other
        applicable terms for the First Notice Space will adjust based on the
        First Notice Rate (defined below). Landlord shall prepare and deliver to
        Tenant an appropriate amendment to the Lease adding the applicable First
        Notice Space to the Leased Premises upon the terms specified in this
        Paragraph 60. Tenant will execute and deliver the amendment to Landlord
        within 10 days after Tenant's receipt of the amendment, and Landlord
        will deliver to Tenant a counterpart of the amendment executed by
        Landlord.

    (e) Landlord is not obligated to offer the First Notice Space to Tenant, and
        Tenant may not exercise its option to lease the First Notice Space, if
        at the time Landlord would otherwise be obligated to give the notice to
        Tenant, Tenant is in default under this Lease.

    (f) The term First Notice Rate means the minimum rent that Landlord quotes
        for space similar to the First Notice Space for a term substantially the
        same as the First Notice Space Lease Term specified by Landlord for the
        First Notice Space, as determined by Landlord in its sole discretion.

    (g) No expansion of the Leased Premises under this Paragraph will extend or
        otherwise modify the Lease Term for the Original Leased Premises. No
        extension of the Lease Term for the Original Leased Premises under
        Paragraph 55 will extend or otherwise modify the applicable Lease Term
        for the First Notice Space added to the Leased Premises under this
        Paragraph 60.

61. Limitation of Actions.
    ---------------------

    Any claim, demand, right, or defense of Tenant arising out of this Lease is
    barred unless Tenant commences an action or asserts an affirmative defense
    within 1 year after the date of the event giving rise to Tenant's claim,
    demand, right, or defense. Tenant represents and warrants to Landlord that
    Tenant has consulted with legal counsel regarding the effect of this
    Paragraph.

62. Year 2000 Readiness Disclosure Statement.
    ----------------------------------------

    (a)    Definitions:  The following terms shall mean as follows:

                                                                         Page 49
<PAGE>

          (1)  Y2K Compliant. A building system, component or service shall be
               considered "Y2K Compliant" if, when used in accordance with its
               documentation, and provided that all other building systems,
               services, and components used with the building system, service,
               or component shall properly exchange accurate date data with it,
               the building system, component or service:

               (A)  Is capable of correctly and accurately processing,
                    providing, or receiving data from, into, and between the
                    20/th/ and 21/st/ centuries, and the years 1999 and 2000 and
                    beyond, including recognizing that the year 2000 is a leap
                    year; and

               (B)  Does not operate abnormally or inaccurately or cease to
                    operate as a result of the inability to correctly and
                    accurately process, provide, or receive date data from,
                    into, and between the 20/th/ and 21/st/ centuries, and the
                    years 1999 and 2000 and beyond.

          (2)  Internal Component. An "Internal Component" means any portion of
               a building system, component, or service that is located within
               the Project and is entirely within the Landlord's control.

    (b)   Representation. Landlord represents and warrants that it is currently
          making good-faith efforts to identify and test the Internal Components
          to determine which are Y2K Compliant, and to remediate, if necessary,
          century date change and date handling deficiencies. Tenant
          acknowledges that Landlord's representations and warranties in this
          Paragraph do not apply to any external infrastructure components
          (including, without limitation, electricity service,
          telecommunications service, service contractors, suppliers, and mail
          service) or internal infrastructure components not entirely within
          Landlord's control.

63. Time: Exercise of Options.
    -------------------------

    Time is of the essence in the exercise of any renewal or expansion options
    granted to Tenant under this Lease. Landlord is not required to give Tenant
    notice of the beginning or end of any time period for Tenant to exercise any
    such option.

64. Execution and Approval of Lease.
    -------------------------------

   Employees and agents of Landlord and Tenant and of Landlord's Broker and
   Tenant's Broker have no authority to make or agree to make a lease or any
   other agreement or undertaking in connection herewith. The submission of this
   Lease for examination and negotiation is not an offer to lease, agreement to
   reserve, or option to lease the Leased Premises. This Lease is effective and
   binding on Landlord only upon the execution and delivery of this Lease by
   Landlord and Tenant.

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<PAGE>

This Lease is executed in multiple originals as of the date first above set
forth.

                                    LANDLORD:

                                    114 MILLENNIUM, LTD., a Texas limited
                                    partnership

                                    By:   T114 Properties, Inc.,
                                          a Delaware corporation, its general
                                          partner



                                         By:  /s/ Leonard Balducci
                                              ----------------------
                                         Name:  Leonard Balducci
                                               ---------------------
                                         Title:  Associate Director
                                                --------------------


                                    TENANT:

                                    DATA RETURN CORPORATION,
                                    a Texas corporation



                                    By:    /s/ Michelle Chambers
                                         ---------------------------
                                         Michelle Chambers,
                                         President and COO

                                                                         Page 51