Document:

<PAGE>

                                                                    EXHIBIT 10.6

                          SEVENTH AMENDMENT TO LEASE
                          --------------------------

     SEVENTH AMENDMENT TO LEASE dated as of this 29/th/ day of March, 1999, by
and between BP PRUCENTER ACQUISITION, LLC, a Delaware limited liability company
(as successor-in-interest to The Prudential Insurance Company of America)
("Landlord") and BRONNER SLOSBERG HUMPHREY, LLC, a Delaware limited liability
company, as successor-in-interest to Bronner Slosberg Humphrey, Inc. ("Tenant").

                                   RECITALS
                                   --------

     By Lease dated May 31, 1995 (as amended by a First Amendment of Lease dated
June 21, 1996, a Second Amendment of Lease dated September 1, 1996, a Third
Amendment of Lease dated November 5, 1996, a Fourth Amendment of Lease dated
January 22, 1997, a Fifth Amendment and Partial Termination of Lease dated July
11, 1997 and a Sixth Amendment and Partial Termination of Lease dated May 15,
1998, the "Lease"), Landlord's predecessor-in-interest did lease to Tenant and
Tenant did hire and lease from Landlord's predecessor-in-interest certain
premises (the "Initial Premises") located in the Tower Building (the
"Building"), Prudential Center, Boston, Massachusetts, which Initial Premises
are described with greater particularity in the Lease.

     Tenant has determined to Lease from Landlord an additional 25,676 square
feet of rentable floor area, consisting of the entirety of the twenty-ninth
(29th) floor of the Building, which space is shown on Exhibit A attached hereto
(the "Seventh Amendment Space").

     Landlord and Tenant are entering into this instrument to set forth said
leasing of the Seventh Amendment Space, to integrate the Seventh Amendment Space
into the Lease and to amend the Lease.

     NOW THEREFORE, in consideration of One Dollar ($1.00) and other good and
valuable consideration in hand this date paid by each of the parties to the
other, the receipt and sufficiency of which are hereby severally acknowledged,
and in further consideration of the mutual promises herein contained, Landlord
and Tenant hereby agree to and with each other as follows:

     1.   Effective as of the "Seventh Amendment Space Commencement Date" (as
          defined in Section 2 hereof) the Seventh Amendment Space shall
          constitute a part of the "Premises" (as defined and used in the
          Lease), so that the Premises (as defined and used in the Lease) shall
          include both the Initial Premises and the Seventh Amendment Space.

     2.   The Seventh Amendment Space Commencement Date shall be earlier to
          occur of (a) the date on which the Seventh Amendment Space is ready
          for occupancy as provided below or (b) the date on which Tenant
          commences beneficial use of the
<PAGE>

          Seventh Amendment Space (Tenant shall be treated as having commenced
          beneficial use when it begins to move furniture and equipment into the
          Seventh Amendment Space for its regular business operation). The
          Seventh Amendment Space shall be deemed to be ready for occupancy at
          such time as Landlord shall have completed the "Asbestos Abatement
          Work" as described on Exhibit B attached hereto and placed the Seventh
          Amendment Space in "shell condition" as described in Exhibit C to the
          above-referenced Fourth Amendment of Lease. Landlord shall give Tenant
          at least thirty (30) days prior written notice of the date on which
          Landlord anticipates that the work to be performed by Landlord
          hereunder will be completed and the Seventh Amendment Space deemed
          ready for occupancy. Notwithstanding the foregoing, under no
          circumstances shall the Seventh Amendment Space Commencement Date be
          deemed to occur prior to March 1, 2001 (unless Tenant has commenced
          beneficial use of the Seventh Amendment Space prior to that date).

          In the event that Landlord shall fail to deliver possession of the
          Seventh Amendment Space with the Asbestos Abatement Work complete and
          the Seventh Amendment Space in shell condition by July 1, 2001 (as
          such date shall automatically be extended for such periods of time as
          Landlord is prevented from delivering the Seventh Amendment Space as
          contemplated herein by reason of events beyond Landlord's reasonable
          control), Tenant shall have the right to terminate the Lease with
          respect to the Seventh Amendment Space only, by giving notice to
          Landlord of Tenant's desire to do so within thirty (30) days after
          such date; and, upon the giving of such notice, the Lease shall
          terminate with respect to the Seventh Amendment Space only, without
          further liability or obligation on the part of either party, unless
          within thirty (30) days after receipt of such termination notice from
          Tenant, Landlord shall so deliver the Seventh Amendment Space in the
          condition required above. Such right of termination shall be Tenant's
          sole and exclusive remedy at law or in equity or otherwise for
          Landlord's failure to deliver the Seventh Amendment Space by July 1,
          2001.

     3.   The Term of the Lease for the Seventh Amendment Space shall commence
          on the Seventh Amendment Space Commencement Date and (notwithstanding
          the fact that the Term of the Lease with respect to the Initial
          Premises may have previously expired as set forth in the Lease) shall
          expire on the last day of the sixtieth (60th) full calendar month
          subsequent to the Seventh Amendment Space Commencement Date (plus the
          partial month, if any, following the Seventh Amendment Space
          Commencement Date) (the "Seventh Amendment Space Lease Term"), unless
          sooner terminated in accordance with the provisions of the Lease as
          herein amended, upon all the same terms and conditions contained in
          the Lease as herein amended.

                                      -2-
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     4.   Rent for the Seventh Amendment Space from the Seventh Amendment Space
          Commencement Date through the expiration of the Seventh Amendment
          Space Lease Term shall be payable at the annual rate of $1,347,990.00
          (being the product of (i) $52.50 and (ii) the rentable floor area of
          the Seventh Amendment Space (being 25,676 square feet)).

     5.   Commencing on the Seventh Amendment Space Commencement Date, Tenant
          shall reimburse Landlord for Increased Operating Expenses (pursuant to
          Section 3.2 of the Lease) for the Seventh Amendment Space in excess of
          the Operating Expenses incurred by Landlord during calendar year 2000
          (being January 1, 2000 through December 31, 2000).

     6.   Commencing on the Seventh Amendment Space Commencement Date, Tenant
          shall reimburse Landlord for increased Real Estate Taxes (pursuant to
          Section 3.4 of the Lease) for the Seventh Amendment Space in excess of
          the Real Estate Taxes paid by Landlord in fiscal year 2001 (being July
          1, 2000 through June 30, 2001).

     7.   Tenant's Share with respect to the Seventh Amendment Space consisting
          of a total of 25,676 rentable square feet will be 2.09%.

     8.   Landlord shall provide approximately four hundred (400) AMPS of
          120/208 volts of electrical power to be used in the Seventh Amendment
          Space and shall, at its sole expense, bring such power to the
          electrical panel serving the Seventh Amendment Space. Tenant shall pay
          for any upgrades to said electric power and shall pay directly to
          Boston Edison Company or other provider of electrical service to the
          Seventh Amendment Space the cost as billed to Tenant for electricity
          used in the Seventh Amendment Space for lighting and office
          receptacles. Notwithstanding the foregoing, Landlord reserves the
          right, to be exercised upon at least thirty (30) days prior written
          notice to Tenant, to install a check meter to measure the consumption
          of electricity in the Seventh Amendment Space. If Landlord shall
          install a check meter as aforesaid, in lieu of making payment directly
          to the utility company, Tenant shall reimburse Landlord monthly in
          arrears within thirty (30) days of receipt of Landlord's invoice for
          the cost of electricity consumed in the Seventh Amendment Space as
          determined by such check meter and Landlord's cost of electricity from
          time to time.

     9.   As provided in the Lease, on the Seventh Amendment Space Commencement
          Date, Tenant shall be entitled to lease, at the then current monthly
          rates, up to thirteen (13) additional parking spaces from the
          Prudential Center garage operator in excess of those currently leased.
          The rate for monthly parking spaces as of

                                      -3-
<PAGE>

          January 1, 1999 is $290.00 per month.

     10.  (A)  Landlord shall provide to Tenant an allowance of $30.00 per
          square foot of rentable floor area of the Seventh Amendment Space (the
          "Tenant Allowance") which may be applied by Tenant upon written notice
          to Landlord to (i) the cost of improvements (including architectural
          and engineering fees in connection therewith) in any portion of the
          Seventh Amendment Space performed by Tenant in accordance with the
          terms of the Lease after Tenant delivers to Landlord paid invoices
          indicating the actual cost of such improvements reasonably
          satisfactory to Landlord or (ii) the actual costs incurred by Landlord
          in connection with any improvement work in the Seventh Amendment Space
          in the event Tenant shall elect to have Landlord perform such work. To
          the extent that the costs of any such work undertaken by Landlord
          exceed the Tenant Allowance, Tenant shall reimburse Landlord, as
          Additional Rent, for such excess upon Tenant's authorization for
          Landlord to proceed with the work attributable thereto.

          If Tenant shall elect for Landlord to perform the improvement work,
          Landlord shall use good faith efforts to perform such work at a
          commercially reasonable cost.

          (B)  Notwithstanding the foregoing, Landlord shall be under no
          obligation to apply any portion of the Tenant Allowance for any
          purposes other than as provided in this Seventh Amendment, nor shall
          Landlord be deemed to have assumed any obligations, in whole or in
          part, of Tenant to any contractors, subcontractors, suppliers, workmen
          or materialmen. In addition, Landlord shall not be obligated to make
          any application of any portion of the Tenant Allowance if (i) there
          shall be existing any default of Tenant under the Lease (as defined in
          Section 8.1) or (ii) there are any liens which are not bonded to the
          reasonable satisfaction of the Landlord against Tenant's interest in
          the Lease or against the Premises, the Building, or the Prudential
          Center arising out of any work performed pursuant to the Lease by
          Tenant or any litigation in which Tenant is a party.

     11.  In accordance with Section 1(F) of the Third Amendment of Lease,
          Tenant has delivered to Landlord an irrevocable standby letter of
          credit in the original face amount of One Million Three Hundred
          Seventy-Five Thousand and 00/100 Dollars ($1,375,000.00) (the "Third
          Amendment LC") to secure, among other obligations of Tenant under the
          Lease, a portion of the transaction costs incurred by Landlord in
          connection with the twenty-fifth (25th) floor of the Building (the
          "Twenty-Fifth Floor"). Section 1(F) also provides in part for the
          yearly reductions of the Third Amendment LC subject to the conditions
          contained in Section 1(F).

                                      -4-
<PAGE>

          Landlord and Tenant agree that Landlord may utilize the Third
          Amendment LC as additional security for Tenant's obligations with
          respect to up to fifty percent (50%) of the Transaction Costs (as
          hereinafter defined) to be incurred by Landlord for the Seventh
          Amendment Space. In order to provide Landlord with sufficient
          additional security for the Transaction Costs for the Seventh
          Amendment Space while preserving Landlord's security for the Twenty-
          Fifth Floor, Landlord and Tenant agree that the Third Amendment LC
          reduction procedures in Section 1(F) are hereby amended to provide
          that, in lieu of the annual fourteen percent (14%) reduction scheduled
          to commence in the first quarter of calendar year 1999, provided the
          Third Amendment Security Reduction Conditions (as that term is defined
          in the Third Amendment of Lease) have been satisfied, the Third
          Amendment LC shall be reduced in each year starting three (3) years
          after the Initial Third Amendment Security Reduction Date specified in
          Section 1(F) (i.e. during the first quarter of calendar year 2002) in
          accordance with the terms and provisions of Section 1(F). For the
          purposes of this Seventh Amendment, the term "Transaction Costs" shall
          mean all costs incurred by Landlord in (i) the negotiation and
          execution of this Seventh Amendment (including, without limitation,
          attorneys' fees), (ii) the preparation of the Seventh Amendment Space
          for Tenant's use and occupancy, including but not limited to the
          Tenant Allowance (but specifically excluding the costs of performing
          the Asbestos Abatement Work and placing the Seventh Amendment Space in
          shell condition, as described in Section 2 above), (iii) real estate
          brokerage commissions and (iv) any unreimbursed costs incurred by
          Landlord's Contract Manager. The Transaction Costs for the Seventh
          Amendment Space are currently calculated to be approximately $36.00
          per rentable square foot of floor area of the Seventh Amendment Space.

          Tenant understands that the exercise of its future expansion rights
          may require a further modification of the terms regarding the
          reduction of the Third Amendment LC and/or an increase in the Third
          Amendment LC to secure a portion of Transaction Costs for such space
          incurred by Landlord. In addition, in the event that Tenant does not
          exercise its option to terminate the Lease with respect to the Seventh
          Amendment Space in accordance with Section 12 below and consequently
          the Seventh Amendment Space Lease Term shall exceed the Term of the
          Lease with respect to the Initial Premises, Landlord shall be entitled
          to retain the then-remaining portion of the Third Amendment LC
          (subject to further reduction in accordance with the terms and
          provisions of Section 1(F) of the Third Amendment of Lease) for the
          balance of the Seventh Amendment Space Lease Term.

          Notwithstanding anything contained herein or in the Third Amendment to
          Lease to the contrary: (i) condition #3 of the Third Amendment
          Security Reduction

                                      -5-
<PAGE>

          Conditions is hereby deleted in its entirety; (ii) the last sentence
          of condition #5(b) of the Third Amendment Security Reduction
          Conditions is hereby deleted in its entirety and the following
          language substituted therefor: "Operating Income is defined as net
          income or loss, excluding one time extraneous items related to the
          recapitalization that occurred in January 1999, plus depreciation,
          interest expenses, amortization, and all Federal, state, local and
          foreign income taxes."; and (iii) condition #5(c) of the Third
          Amendment Security Reduction Conditions is hereby deleted in its
          entirety and the following language substituted therefor: "TENANT'S
          third party debt service expense exceeds 25% of TENANT'S net income on
          an annual basis."

     12.  In accordance with Section 12.14 of the Lease (as amended by Section 9
          of the First Amendment of Lease), Tenant has delivered to Landlord an
          irrevocable standby letter of credit in the original face amount of
          Four Million Seventy-Eight Thousand and 00/100 Dollars ($4,078,000.00)
          (the "Original LC") to secure, among other things, a portion of the
          Lease Transaction Costs incurred by Landlord in connection with the
          Initial Premises and the First Amendment Spaces. Section 12.14 (as
          amended by Section 9 of the First Amendment of Lease) also provides in
          part for yearly reductions of the Original LC subject to the
          conditions contained in Section 12.14 and Section 9.

          Notwithstanding anything contained in said Section 12.14 and Section 9
          to the contrary, Landlord and Tenant hereby agree that: (i) the
          Original LC shall be reduced by Eight Hundred Thousand and 00/100
          Dollars ($800,000.00) on or about the date of this Seventh Amendment,
          which such reduction shall be in lieu of any other reductions to the
          Original LC contemplated by or scheduled to take place under the Lease
          prior to December 31, 1998; (ii) the Original LC shall be further
          reduced by an additional Eight Hundred Thousand and 00/100 Dollars
          ($800,000.00) during the second quarter of calendar year 1999, which
          such reduction shall be in lieu of any other reduction to the Original
          LC contemplated by or scheduled to take place under the Lease during
          calendar year 1999; and (iii) commencing in the first quarter of
          calendar year 2000, and provided that in each instance the L.C.
          Reduction Conditions (as that term is defined in the Lease) have been
          satisfied, the Original LC shall be reduced in each year by the amount
          shown for each applicable lease year on the schedule set forth in
          Exhibit LCR attached to and made a part of this Seventh Amendment
          (which such Exhibit LCR shall replace and supercede Exhibit LCR
          attached to the First Amendment of Lease).

          Notwithstanding anything contained herein or in the Lease to the
          contrary: (i) condition #3 of the L.C. Reduction Conditions is hereby
          deleted in its entirety; (ii) the last sentence of condition #5(b) of
          the L.C. Reduction Conditions is hereby deleted in its entirety and
          the following language substituted therefor: "Operating Income is
          defined as net income or loss, excluding one time extraneous items
          related to the recapitalization that occurred in January 1999, plus
          depreciation, interest expenses, amortization, and all Federal, state,
          local and foreign income taxes."; and (iii)

                                      -6-
<PAGE>

          condition #5(c) of the L.C. Reduction Conditions is hereby deleted in
          its entirety and the following language substituted therefor:
          "TENANT'S third party debt service expense exceeds 25% of TENANT'S net
          income on an annual basis."

     13.  By written notice ("Tenant's Termination Notice") given by Tenant to
          Landlord at any time during the Seventh Amendment Space Lease Term on
          or before the last day of the month which is twelve (12) months prior
          to the expiration of the Lease Term with respect to the Initial
          Premises, Tenant may elect to cancel and terminate the Lease with
          respect to the Seventh Amendment Space effective on the last day of
          the Lease Term with respect to the Initial Premises (the "Seventh
          Amendment Space Early Termination Date") but not before or after said
          date; provided, however, that as a condition precedent to such
          cancellation and termination, Tenant must deliver to Landlord together
          with Tenant's Termination Notice good funds in an amount equal to
          "Tenant's Termination Payment" (as defined below) and provided further
          that notwithstanding such termination and as a further condition
          precedent thereto, (i) Tenant shall pay to Landlord on a timely basis
          all Rent and payments on account of Increased Operating Expenses,
          increased Real Estate Taxes, utility charges and all additional rent
          and other amounts due from Tenant (including, but not limited to, all
          past due amounts thereof) through the Seventh Amendment Space Early
          Termination Date (it being acknowledged and agreed that Tenant's
          Termination Payment is in addition to such amounts and no credit shall
          be given towards the payment of such amount on account of the payment
          of Tenant's Termination Payment), (ii) there shall be no default
          (beyond any applicable notice and cure period) on the part of Tenant
          under the Lease on either the date Tenant gives Tenant's Termination
          Notice or on the Seventh Amendment Space Early Termination Date and
          (iii) Tenant shall quit and vacate the Seventh Amendment Space as of
          the Seventh Amendment Space Early Termination Date and surrender the
          same in the condition required by the applicable provisions of the
          Lease. In the event that Tenant's share of such Increased Operating
          Expenses, increased Real Estate Taxes, utility charges and such other
          additional rent and other amounts due through the Seventh Amendment
          Space Early Termination Date is not finally determined as of the
          Seventh Amendment Space Early Termination Date, Tenant shall make
          payment on account as reasonably estimated by Landlord if so requested
          by Landlord and in any event Tenant shall make final payment of
          amounts due through the Seventh Amendment Space Early Termination Date
          within thirty (30) days after final billing therefor by Landlord. The
          obligations of Tenant set forth in this Section 12 shall survive the
          termination of the Lease. If Tenant shall not give to Landlord
          Tenant's Termination Notice as provided in this Section 13 (time being
          of the essence), the provisions of this Section 13 shall be deemed
          null and void. "Tenant's Termination Payment" shall be equal to the
          product of(a) the "Fixed Monthly Amortization Amount" as defined
          hereinbelow and (b) the number of

                                      -7-
<PAGE>

          months that would have remained in the Seventh Amendment Space Lease
          Term from and after the Seventh Amendment Space Early Termination Date
          but for the giving by Tenant of the Tenant's Termination Notice. The
          "Fixed Monthly Amortization Amount" shall equal the monthly payment on
          a direct reduction loan basis amortized monthly where (i) the
          principal amount is equal to the Tenant Allowance plus the commission
          paid by Landlord to the Recognized Broker (as hereinafter defined) in
          connection with this Seventh Amendment (the "Broker's Commission"),
          (ii) the term is sixty (60) calendar months and (iii) the monthly
          interest rate is 0.8333%.

     14.  Landlord shall have the right, at any time prior to the Seventh
          Amendment Space Commencement Date, to substitute for the Seventh
          Amendment Space either the twenty-fourth (24th), twenty-sixth (26th)
          or twenty-seventh (27th) floor of the Building in accordance with the
          following:

          a..  Landlord shall give Tenant at least one hundred twenty (120) days
               written notice of Landlord's intention to substitute one of the
               aforesaid floors for the Seventh Amendment Space.

          b.   Landlord shall reimburse Tenant for any reasonable costs incurred
               by Tenant in readapting Tenant's architectural and engineering
               plans to the extent necessary as a result of the substitution of
               a different floor of the Building for the original Seventh
               Amendment Space described herein.

          c.   Upon the delivery of the notice described in subsection (a)
               above, the new premises shall become the "Seventh Amendment
               Space" for the purposes of the Lease as amended by this Seventh
               Amendment, and the parties hereto shall execute an amendment to
               the Lease setting forth the substitution for the original Seventh
               Amendment Space.

          d.   Notwithstanding the provisions of Section 2 above, in the event
               that the new Seventh Amendment Space is to be located on a floor
               in the Building on which Asbestos Abatement Work has already been
               performed prior to the date of Landlord's notice of substitution,
               Landlord shall deliver such space to Tenant in "as is" condition,
               broom clean and clear of all occupants. If the new Seventh
               Amendment Space is to be located on a floor in the Building in
               which Asbestos Abatement Work has not already been performed,
               Landlord shall deliver such space after performing the work
               described in Section 2.

          e.   The rentable floor area of the new Seventh Amendment Space shall
               not vary by more than five hundred (500) square feet from the
               rentable floor

                                      -8-
<PAGE>

               area of the original Seventh Amendment Space (being 25,676 square
               feet). Rent and additional rent for the new Seventh Amendment
               Space shall in any event be based on the actual rentable floor
               area of such space.

     15.  Tenant hereby acknowledges and confirms that the indemnity set forth
          in Section 11.1 of the Lease shall apply, and always has applied, to
          the use or occupancy by Tenant of the Premises in its entirety and to
          the acts or omissions of Tenant, its agents, employees or any
          contractors brought onto the Premises in its entirety by Tenant.

     16.  (A)  Tenant warrants and represents that Tenant has not dealt with any
          broker in connection with the consummation of this Seventh Amendment
          other than Meredith & Grew, Incorporated (the "Recognized Broker");
          and in the event any claim is made against Landlord relative to
          dealings by Tenant with brokers other than the Recognized Broker,
          Tenant shall defend the claim against Landlord with counsel of
          Tenant's selection first approved by Landlord (which approval will not
          be unreasonably withheld) and save harmless and indemnify Landlord on
          account of loss, cost or damage which may arise by reason of such
          claim.

          (B)  Landlord warrants and represents that Landlord has not dealt with
          any broker in connection with the consummation of this Seventh
          Amendment other than the Recognized Broker; and in the event any claim
          is made against Tenant relative to dealings by Landlord with brokers
          other than the Recognized Broker, Landlord shall defend the claim
          against Tenant with counsel of Landlord's selection and save harmless
          and indemnify Tenant on account of loss, cost or damage which may
          arise by reason of such claim. Landlord shall be responsible for
          paying the commission due to the Recognized Broker in connection with
          this Seventh Amendment.

     17.  Except as otherwise expressly provided herein, all capitalized terms
          used herein without definition shall have the same meanings as are set
          forth in the Lease.

     18.  Except as herein amended the Lease shall remain unchanged and in full
          force and effect. All references to the "Lease" shall be deemed to be
          references to the Lease as herein amended.

                                      -9-
<PAGE>

??? as a sealed instrument as of the date and year first above written.

                  LANDLORD:

Cameron
-------
                  BP PRUCENTER ACQUISITION, LLC

                  By:  BOSTON PROPERTIES LIMITED PARTNERSHIP, its Manager

                       By:  BOSTON PROPERTIES, INC.,
                            its general partner

                            By /s/ Claude B. Hoopes
                               ------------------------
                            Name Claude B. Hoopes
                                 ----------------------
                            Title Vice President
                                  ---------------------

                       TENANT:

                       BRONNER SLOSBERG
                       HUMPHREY LLC
                       By:  BSH Holding, LLC, its manager

                       By:  Bronner Slosberg Humphrey Co., its Manager
                            -------------------------

                            By /s/ Meryl K. Beckingham
                               ------------------------
                            Name Meryl K. Beckingham
                                 ----------------------
                            Title SVP/CFO
                                 ----------------------

                                      -10-
<PAGE>

                                   EXHIBIT B
                                   ---------

1.  Overview
    --------

     A.   This agreement consists of providing the work required for selective
          demolition, asbestos removal, and replacement fireproofing at the
          29/th/ floor Prudential Tower, Prudential Center, Boston,
          Massachusetts

2.   Description of Work
     -------------------

     The following is a brief description of the work included under this
     agreement.

     Work covered by Contract Documents:

     1.   Selective Demolition:
             a.)    Removal of carpet
             b.)    Removal of below ceiling wall partitions
             c.)    Removal of freight and passenger elevator lobby ceilings
             d.)    Removal of core storage room ceiling
             e.)    Removal of travertine wall panels in passenger elevator
                    lobby

     2.   Removal of Asbestos and Hazardous Materials:
             a.)    Removal of all suspended ceiling as acm
             b.)    Removal of all light fixtures as acm
             c.)    Removal of light fixtures ballasts as PCB-containing
             d.)    Removal of all HVAC ductwork and related mechanical
                    components located above ceiling as acm
             e.)    Removal of abandoned electrical and communication system
                    wiring, conduit, etc.
             f.)    Removal of all insulation on building mechanical systems
                    located above ceiling as acm
             g.)    Removal of structural fireproofing as acm (--80% amosite)
             h.)    Removal of all interior column enclosures and associated
                    masonry blocks as acm
             i.)    Removal of all floor tile and associated mastic as acm
                    using chemical stripping methods
             j.)    Cleaning of all surfaces

     3.   Replacements
             a.)    Replacement of structural fireproofing

     4.   Firewatch
             a.)    Provide 24-hour firewatch throughout the Contract Period.

<PAGE>

                    EXHIBIT LCR

              Original LC      LC        Total LC
   Year         Balance     Reduction     Balance
   ------------------------------------------------
   1999        4,078,000    1,600,000    2,478,000
   2000        2,478,000      450,000    2,028,000
   2001        2,028,000      450,000    1,578,000
   2002        1,578,000      450,000    1,128,000
   2003        1,128,000      450,000      678,000
   2004          678,000      450,000      228,000
   2005          228,000      228,000            0

   1. Original Standby letter of Credit

   2. Straightline declining balance over life of lease

   3. Original Standby letter of Credit Balance for lease year.<PAGE>

                                                                   EXHIBIT 10.7

                           EIGHTH AMENDMENT TO LEASE
                           -------------------------

     EIGHTH AMENDMENT TO LEASE dated as of this 30/th/ day of July, 1999, by and
between BP PRUCENTER ACQUISITION, LLC, a Delaware limited liability company (as
successor-in-interest to The Prudential Insurance Company of America)
("Landlord") and BRONNERCOM, LLC, formerly known as BRONNER SLOSBERG HUMPHREY,
LLC, a Delaware limited liability company, as successor-in-interest to Bronner
Slosberg Humphrey, Inc. ("Tenant").

                                   RECITALS
                                   --------
     By Lease dated May 31, 1995, as amended by a First Amendment of Lease dated
June 21, 1996, a Second Amendment of Lease dated September 1, 1996, a Third
Amendment of Lease dated November 5, 1996, a Fourth Amendment of Lease dated
January 22,1997, a Fifth Amendment and Partial Termination of Lease dated July
11, 1997, a Sixth Amendment and Partial Termination of Lease dated May 15, 1998
and a Seventh Amendment to Lease dated March 29, 1999 (the "Lease"), Landlord's
predecessor-in-interest did lease to Tenant and Tenant did hire and lease from
Landlord's predecessor-in-interest certain premises (the "Initial Premises")
located in the Tower Building (the "Building"), Prudential Center, Boston,
Massachusetts, which Initial Premises are described with greater particularity
in the Lease.

     Tenant has determined to lease from Landlord 2,020 square feet of rentable
floor area on the fifth (5/th/) floor of the Building, pursuant to Paragraph 5
of the First Amendment of Lease and referred to therein as the "Pru Timber
Space", which space is shown hatched on Exhibit A attached hereto (the "Eighth
Amendment Space A").

     Tenant has determined to lease from Landlord 1,518 square feet of rentable
floor area on the fifth (5/th/) floor of the Building, pursuant to Paragraph 5
of the First Amendment of Lease and referred to therein as the "Waterhouse"
space, which space is shown cross-hatched on Exhibit A attached hereto (the
"Eighth Amendment Space B").

     Landlord and Tenant are entering into this instrument to set forth said
leasing of the Eighth Amendment Space A and the Eighth Amendment Space B, to
integrate the Eighth Amendment Space A and Eighth Amendment Space B into the
Lease and to amend the Lease.

     NOW THEREFORE, in consideration of One Dollar ($1.00) and other good and
valuable consideration in hand this date paid by each of the parties to the
other, the receipt and sufficiency of which are hereby severally acknowledged,
and in further consideration of the mutual promises herein contained, Landlord
and Tenant hereby agree to and with each other as follows:

     A. EIGHTH AMENDMENT SPACE A
<PAGE>

     1.   Effective as of the "Eighth Amendment Space A Commencement Date" (as
          defined in Section 3 hereof) the Eighth Amendment Space A shall
          constitute a part of the "Premises" (as defined and used in the
          Lease), so that the Premises (as defined and used in the Lease) shall
          include the Initial Premises and the Eighth Amendment Space A.

     2.   The Eighth Amendment Space A Commencement Date shall be June 1, 1999
          (i.e., the date on which Tenant commenced beneficial use of the Eighth
          Amendment Space A). The parties acknowledge that, prior to the Eighth
          Amendment Space A Commencement Date, Landlord repainted the Eighth
          Amendment Space A, shampooed the carpeting therein and delivered the
          Eighth Amendment Space A to Tenant vacant, in broom-clean condition
          and in a condition which was at least as good as shell condition, as
          required by Paragraph 5 of the First Amendment of Lease and that
          Tenant has accepted the Eighth Amendment Space A in the condition in
          which it was delivered on the Eighth Amendment Space A Commencement
          Date. Notwithstanding anything to the contrary herein or in the Lease
          contained, Landlord has no obligation to perform any other work in the
          Eighth Amendment Space A or to provide to Tenant any allowance in
          respect of the Eighth Amendment Space A.

     3.   The Term of the Lease for the Eighth Amendment Space A shall commence
          on the Eighth Amendment Space A Commencement Date and shall expire on
          November 30, 2005, unless sooner terminated in accordance with the
          provisions of the Lease as herein amended, upon all the same terms and
          conditions contained in the Lease as herein amended.

     4.   Rent for the Eighth Amendment Space A from the Eighth Amendment Space
          A Commencement Date through the expiration of the Eighth Amendment
          Space A Lease Term shall be payable at the annual rate of $80,800.00
          (being the product of (i) $40.00 and (ii) the rentable floor area of
          the Eighth Amendment Space A (being 2,020 square feet).

     5.   Commencing on the Eighth Amendment Space A Commencement Date, Tenant
          shall reimburse Landlord for Increased Operating Expenses (pursuant to
          Section 3.2 of the Lease) for the Eighth Amendment Space A in excess
          of the Operating Expenses incurred by Landlord during calendar year
          1999 (being January 1, 1999 through December 31, 1999).

     6.   Commencing on the Eighth Amendment Space A Commencement Date, Tenant
          shall reimburse Landlord for increased Real Estate Taxes (pursuant to
          Section 3.4 of the Lease) for the Eighth Amendment Space A in excess
          of the Real Estate Taxes paid by Landlord in fiscal year 2000 (being
          July 1, 1999

                                      -2-
<PAGE>

          through June 30, 2000).

     7.   Tenant's Share with respect to the Eighth Amendment Space A consisting
          of a total of 2,020 rentable square feet will be .16%.

     8.   Tenant shall reimburse Landlord monthly in arrears within thirty (30)
          days of receipt of Landlord's invoice for the cost of electricity
          consumed in the Eighth Amendment Space A as determined by a check
          meter (which check meter is presently installed) and Landlord's cost
          of electricity from time to time.

     9.   Tenant shall not be entitled to any additional parking passes in
          connection with Tenant's demise of the Eighth Amendment Space A.

     10.  Tenant's extension rights set forth in Section 12.15 of the Lease, as
          amended by Section II(1) of the Fourth Amendment of Lease, shall apply
          to the Eighth Amendment Space A.

     11.  There shall be no modification of the terms regarding the reduction
          and/or increase in the Original LC and/or the Third Amendment LC in
          connection with Tenant's demise of the Eighth Amendment Space A.

     12.  Notwithstanding anything to the contrary herein or in the Lease
          contained, if, during the term of the Lease in respect of Eighth
          Amendment Space A, Tenant elects to remove the existing carpeting and
          install new carpeting in the Eighth Amendment Space A and/or to
          replace the original building column enclosures within the Eighth
          Amendment Space A (collectively, "Tenant's Space A Work"), Landlord
          shall, at Landlord's cost, during the performance of Tenant's Space A
          Work, remove the floor tile and mastic from the Eighth Amendment Space
          A and, to the extent that the building columns contain asbestos
          containing material ("ACM"), remove the ACM from the columns to the
          extent required by applicable laws ("Landlord's Space A Removal
          Work"). Landlord shall coordinate the Landlord's Space A Removal Work
          with Tenant's Space A Work. In no event shall Tenant be entitled to
          any diminution in rental value in respect of the Eighth Amendment
          Space A on account of the performance of Landlord's Space A Removal
          Work.

     B.   EIGHTH AMENDMENT SPACE B

     1.   Effective as of the "Eighth Amendment Space B Commencement Date" (as
          defined in Section 4 hereof) the Eighth Amendment Space B shall
          constitute a part of the part of the "Premises" (as defined and used
          in the Lease), so that the Premises (as defined and used in the Lease)
          shall include the Initial Premises, the Eighth Amendment Space A and
          the Eighth Amendment Space

                                      -3-
<PAGE>

          B.

     2.   The Eighth Amendment Space B Commencement Date shall be the earlier to
          occur of (a) the date on which the Eighth Amendment Space B is ready
          for occupancy as provided below or (b) the date on which Tenant
          commences beneficial use of the Eighth Amendment Space B (Tenant shall
          be treated as having commenced beneficial use when it begins to move
          furniture and equipment into the Eighth Amendment Space B for its
          regular business operation). The Eighth Amendment Space B shall be
          deemed to be ready for occupancy at such time as Landlord shall, at
          Landlord's cost, have completed repainting and recarpeting the Eighth
          Amendment Space B using Building standard paint and carpeting and
          removal of the floor tiles and mastic from the Eighth Amendment Space
          B (the "Eighth Amendment Space B Landlord Work") and delivered the
          Eighth Amendment Space B to Tenant vacant and in broom-clean condition
          and in a condition which is at least as good as shell condition, as
          required by Paragraph 5 of the First Amendment of Lease. Tenant shall,
          on or before November 30, 1999, advise Landlord of the color
          selections required by Landlord in order to commence the Eighth
          Amendment Space B Landlord Work. Landlord shall use reasonable efforts
          to complete the Eighth Amendment Space B Landlord Work on or before
          February 1, 2000. If the Eighth Amendment Space B is not ready for
          occupancy on or before April 1, 2000, then Tenant shall have the
          right, upon written notice to Landlord given on or after April 1, 2000
          but on or before the date that the Eighth Amendment Space B is ready
          for occupancy, to cancel Tenant's exercise of its option to lease the
          Eighth Amendment Space B, effective as of the date of such notice. If
          Tenant fails timely to make the color selections required by Landlord
          in order to commence the Eighth Amendment Space B Landlord Work, then,
          notwithstanding anything to the contrary herein contained, (i) the
          Eighth Amendment Space B Commencement Date shall be the earlier to
          occur of (a) February 1, 2000 or (b) the date on which Tenant
          commences beneficial use of the Eighth Amendment Space B, (ii) Tenant
          shall have no right to cancel Tenant's exercise of its option to lease
          the Eighth Amendment Space B pursuant to the immediately preceding
          sentence on account of Landlord's failure to perform the Eighth
          Amendment Space B Landlord Work, (iii) Landlord shall complete the
          Eighth Amendment Space B Landlord Work promptly after Tenant makes
          such color selections and (iv) Landlord shall deliver the Eighth
          Amendment Space B to Tenant in the condition and within the time-frame
          otherwise required by this Paragraph B.2. If Landlord is required to
          perform the Eighth Amendment Space B Landlord Work after the Eighth
          Amendment Space B is delivered to Tenant pursuant to the immediately
          preceding sentence, Tenant agrees to cooperate with Landlord during
          the performance of the Eighth Amendment Space B Work and Tenant shall,
          upon billing therefor, as additional rent, reimburse Landlord for any

                                      -4-
<PAGE>

          overtime or other premium costs incurred by Landlord in connection
          with the performance of the Eighth Amendment Space B Work which costs
          would not have been incurred by Landlord had Landlord performed the
          Eighth Amendment Space B Work prior to delivering the Eighth Amendment
          Space B to Tenant.

     3.   The Term of the Lease for the Eighth Amendment Space B shall commence
          on the Eighth Amendment Space B Commencement Date and shall expire on
          November 30, 2005, unless sooner terminated in accordance with the
          provisions of the Lease as herein amended, upon all the same terms and
          conditions contained in the Lease as herein amended.

     4.   Rent for the Eighth Amendment Space B from the Eighth Amendment Space
          B Commencement Date through the expiration of the Eighth Amendment
          Space B Lease Term shall be payable at the annual rate of $60,720.00
          (being the product of (i) $40.00 and (ii) the rentable floor area of
          the Eighth Amendment Space B (being 1,518 square feet).

     5.   Commencing on the Eighth Amendment Space B Commencement Date, Tenant
          shall reimburse Landlord for Increased Operating Expenses (pursuant to
          Section 3.2 of the Lease) for the Eighth Amendment Space B in excess
          of the Operating Expenses incurred by Landlord during calendar year
          1999 (being January 1, 1999 through December 31, 1999).

     6.   Commencing on the Eighth Amendment Space B Commencement Date, Tenant
          shall reimburse Landlord for increased Real Estate Taxes (pursuant to
          Section 3.4 of the Lease) for the Eighth Amendment Space B in excess
          of the Real Estate Taxes paid by Landlord in fiscal year 2000 (being
          July 1, 1999 through June 30, 2000).

     7.   Tenant's Share with respect to the Eighth Amendment Space B consisting
          of a total of 1,518 rentable square feet will be .12%.

     8.   Tenant shall reimburse Landlord monthly in arrears within thirty (30)
          days of receipt of Landlord's invoice for the cost of electricity
          consumed in the Eighth Amendment Space B as determined by a check
          meter (which check meter is presently installed) and Landlord's cost
          of electricity from time to time.

     9.   Tenant shall not be entitled to any additional parking passes in
          connection with Tenant's demise of the Eighth Amendment Space B.

     10.  Tenant's extension rights set forth in Section 12.15 of the Lease, as
          amended by Section II(1) of the Fourth Amendment of Lease, shall apply
          to the Eighth

                                      -5-
<PAGE>

          Amendment Space B.

     11.  There shall be no modification of the terms regarding the reduction
          and/or increase in the Original LC and/or the Third Amendment LC in
          connection with Tenant's demise of the Eighth Amendment Space B.

     12.  Notwithstanding anything to the contrary herein or in the Lease
          contained, if, during the term of the Lease in respect of Eighth
          Amendment Space B, Tenant elects to replace the original building
          column enclosures within the Eighth Amendment Space B (collectively,
          "Tenant's Space B Work"), to the extent that the building columns
          contain asbestos containing material ("ACM"), Landlord shall, at
          Landlord's cost, during the performance of Tenant's Space B Work,
          remove the ACM from the columns to the extent required by applicable
          laws ("Landlord's Space B Removal Work"). Landlord shall coordinate
          the Landlord's Space B Removal Work with Tenant's Space B Work. In no
          event shall Tenant be entitled to any diminution in rental value in
          respect of the Eighth Amendment Space B on account of the performance
          of Landlord's Space B Removal Work.

     C.   RIGHT OF FIRST OFFER

     Subject to the rights of the existing tenant of a portion of the First
Offer Space, as hereinafter defined, and the rights of another tenant in the
Building, MCI Telecommunications Corporation to lease the First Offer Space, all
of which rights are prior to the rights of Tenant under this Paragraph C, and
provided that at the time the First Offer Space first becomes available for
reletting (i) Tenant is not in default, beyond the expiration of applicable
notice and grace periods, of any of its obligations under the Lease, (ii) Tenant
has not assigned the Lease or sublet more than thirty percent (30%) of the
Premises then demised to Tenant (other than an assignment or subletting pursuant
to the last sentence of Section 5.2 of the Lease) and (ii) the Lease is still in
full force and effect, Landlord agrees not to enter into a lease or leases to
relet the First Offer Space or any portion thereof without first giving to
Tenant an opportunity to lease such space as hereinafter set forth. For the
purposes of this Paragraph C, the "First Offer Space" shall be defined as the
balance of the fifth (5/th/) floor of the Building which is not leased to
Tenant, containing 3,298 rentable square feet, substantially as shown on Exhibit
A attached hereto. When such First Offer Space becomes available for reletting,
Landlord shall notify Tenant ("Landlord's Notice") of the availability of such
space and shall advise Tenant of the business terms upon which Landlord is
willing so to lease such space, except that the rent and other economic terms
with respect to the First Offer Space shall be ninety-five percent (95%) of the
then fair market rental and the term of the Lease in respect of the First Offer
Space shall expire on November 30, 2005, unless sooner terminated or extended in
accordance with the provisions of the Lease as herein amended (it being
understood that Tenant's extension rights set forth in Section 12.15 of the
Lease, as amended by Section II(1) of the Fourth Amendment of Lease, shall apply
to the

                                      -6-
<PAGE>

First Offer Space). If Tenant wishes to exercise Tenant's right of first offer,
Tenant shall do so, if at all, by giving Landlord written notice of Tenant's
desire to lease such space (Tenant having no right to lease less than the entire
amount of such First Offer Space offered to Tenant) on such terms within ten
(10) business days after receipt of Landlord's Notice to Tenant of the
availability of such space and of such terms. If Tenant shall give such notice,
the same shall constitute an agreement to enter into an amendment to the Lease
to incorporate the entire amount of such First Offer Space into the Premises
demised under the Lease within thirty (30) days after Tenant's notice to
Landlord. If Tenant shall not so exercise such right within such ten (10)
business day period or Landlord and Tenant shall not execute an amendment to the
Lease to incorporate the First Offer Space into the Premises within thirty (30)
days of Tenant's exercise of such right, time being of the essence, Tenant shall
have no further right of first offer hereunder.

     D.   OTHER TERMS

     1.   Tenant hereby acknowledges and confirms that the indemnity set forth
          in Section 11.1 of the Lease shall apply, and always has applied, to
          the use or occupancy by Tenant of the Premises in its entirety and to
          the acts or omissions of Tenant, its agents, employees or any
          contractors brought onto the Premises in its entirety by Tenant.

     2.   (A) Tenant warrants and represents that Tenant has not dealt with any
          broker in connection with the consummation of this Eighth Amendment
          other than Meredith & Grew, Incorporated (the "Recognized Broker");
          and in the event any claim is made against Landlord relative to
          dealings by Tenant with brokers other than the Recognized Broker,
          Tenant shall defend the claim against Landlord with counsel of
          Tenant's selection first approved by Landlord (which approval will not
          be unreasonably withheld) and save harmless and indemnify Landlord on
          account of loss, cost or damage which may arise by reason of such
          claim.

          (B) Landlord warrants and represents that Landlord has not dealt with
          any broker in connection with the consummation of this Eighth
          Amendment other than the Recognized Broker; and in the event any claim
          is made against Tenant relative to dealings by Landlord with brokers
          other than the Recognized Broker, Landlord shall defend the claim
          against Tenant with counsel of Landlord's selection and save harmless
          and indemnify Tenant on account of loss, cost or damage which may
          arise by reason of such claim. Landlord shall be responsible for
          paying the commission due to the Recognized Broker in connection with
          this Eighth Amendment.

     3.   Except as otherwise expressly provided herein, all capitalized terms
          used herein without definition shall have the same meanings as are set
          forth in the

                                      -7-
<PAGE>

          Lease.

     4.   Except as herein amended the Lease shall remain unchanged and in full
          force and effect. All references to the "Lease" shall be deemed to be
          references to the Lease as herein amended.

     EXECUTED as a sealed instrument as of the date and year first above
written.

WITNESS:                              LANDLORD:

____________________________          BP PRUCENTER ACQUISITION, LLC

                                      By:  BOSTON PROPERTIES LIMITED
                                           PARTNERSHIP, its Manager

                                           By:  BOSTON PROPERTIES, INC.,
                                                its general partner

                                                By  /s/ Claude B. Hoopes
                                                  ----------------------
                                                Name  Claude B. Hoopes
                                                    --------------------
                                                Title  Vice President
                                                     -------------------

WITNESS:                              TENANT:

  /s/ M. Mosley-Jones                 BRONNERCOM, LLC
------------------------------
                                      By:  BSH Holding, LLC, its Manager

                                           By:  Bronner Slosberg
                                                Humphrey Co., its
                                                Manager

                                                By  /s/ Meryl K. Beckingham
                                                  -------------------------
                                                Name  Meryl K. Beckingham
                                                    -----------------------
                                                Title  EVP
                                                     ----------------------

                                      -8-
<PAGE>

                                   EXHIBIT A

                                   [DIAGRAM]

                   5TH FLOOR PRUDENTIAL TOWER - RENTAL PLAN

                            TOTAL FLOOR (New York)
                                 18,834 usable
                                24,501 rentable
                             The Prudential Center

<PAGE>

                                   EXHIBIT A

                                   [Diagram]

                           Bronner Slosberg Humphrey
                   5th Floor Prudential Tower -- Rental Plan
                            Total Floor (New York)
                                 18,834 usable
                                24,501 rentable

                                      -10-

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