<PAGE>

                                                                   Exhibit 10.76
                      ASSIGNMENT AND ASSUMPTION OF LEASE

     THIS ASSIGNMENT AND ASSUMPTION OF LEASE AGREEMENT (the "Assignment") dated
as of February 28, 2001 (the "Assignment Date") is made and entered into by and
between The Gaithersburg Realty Trust, a Delaware business trust (the
"Assignor"), and SFHI, LLC, a Delaware limited liability company (the
"Assignee").

     WHEREAS, Assignor is a party to that certain lease of real property
described in Exhibit "A" attached hereto (the "Land") by and between REII-
Gaithersburg, Maryland, L.L.C. ("REII"), as landlord, and GE Information
Services, Inc. ("GEIS"), as tenant, dated for reference purposes only as of
January 28, 1999, as assigned by REII to Assignor (the "Lease"); and

     WHEREAS, Assignor has sold and conveyed the Land to Assignee pursuant to
the terms and conditions of a purchase contract by and between Assignor and
Assignee having an effective date of January 9, 2001 (the "Contract"); and

     WHEREAS, Assignor desires to assign the Lease to Assignee and Assignee
desires to assume the rights, duties and obligations of Assignor thereunder.

     NOW THEREFORE, in the consideration of the foregoing recitals, the
covenants and agreements herein contained, and for other good and valuable
consideration exchanged between them, the parties agree as follows:

     1.  Assignment and Assumption.  Assignor hereby assigns to Assignee and
         -------------------------
Assignee hereby accepts and assumes from Assignor all of Assignor's right, title
and interest in, to and under the Lease, subject to the terms and conditions
herein set forth and effective on the Assignment Date. Assignee agrees to
undertake, perform, defend and discharge each and every duty, obligation and
liability of Assignor arising under or with respect to the Lease from and after
the Assignment Date in accordance with the terms thereof.  Assignee shall have
and possess all of the rights and privileges of the landlord under the Lease on
and after the Assignment Date.

     2.  Authority.  Assignor and Assignee each represent and warrant that: (a)
         ---------
it has full power and authority to execute, deliver and perform this Assignment;
(b) the execution, delivery and performance of this Assignment has been duly
authorized by its Board of Directors or applicable governing body and does not
require further authorization or consent from any other person or entity; and
(c) the Assignment has been duly authorized, executed and delivered and is
enforceable in accordance with its terms, except as such legality, validity
binding effect or enforcement may be limited by bankruptcy, insolvency or
similar laws effecting creditor's rights generally or by equitable principles
relating to the availability of remedies.
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     3.  Assignor's Warranties and Certification.  This Assignment is made with
         ----------------------------------------
full warranties of title by Assignor and Assignor warrants that there are no
prior assignments or pledges of the Lease except for those assignments and
pledges for security purposes that are being released in their entirety
concurrently with the delivery of this Assignment.  Assignor hereby certifies
that Lease attached hereto as Exhibit "B" is a true and complete original
counterpart of the Lease and all amendments thereto, containing all rights and
obligations between landlord and tenant with respect to the subject property.

     4.  Notice to Tenant under the Lease.  Assignor and Assignee shall jointly
         --------------------------------
notify the tenant and all other parties requiring notice under the Lease of this
Assignment and Assignee shall provide such parties with an address for receipt
of notices under the Lease in accordance with the terms thereof.

     5.  Governing Law.  This Assignment shall be governed and construed in
         -------------
accordance with the laws of the State of Maryland without reference to its
conflicts of laws principles.

     6.  Counterparts.  This Assignment may be executed in two or more
         ------------
counterparts, all of which when taken together shall constitute one and the same
instrument.

     7.  No Modification of Contract.    This Assignment is entered into and
         ---------------------------
delivered by the parties pursuant to the terms and conditions set forth in the
Contract and nothing contained in this Assignment shall be construed to limit,
terminate or expand the representations, warranties and covenants set forth in
the Contract, all of which shall survive the delivery of this Assignment to the
full extent provided in the Contract.


                     [SIGNATURES APPEAR ON FOLLOWING PAGE]

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     IN WITNESS WHEREOF, the parties have caused this Assignment to be executed
the day and year first above written.

                              ASSIGNOR:
                              --------

                              THE GAITHERSBURG REALTY TRUST


                              By: /s/ David H. Bralove
                              ------------------------
                              David H. Bralove, not individually but solely in
                              his capacity as Owner Trustee of The Gaithersburg
                              Realty Trust



                              ASSIGNEE:
                              --------

                              SFHI, LLC

                              By: /s/ Paul W. Lowden

                              Name: Paul W. Lowden

                              Title: Chairman of the Board

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<PAGE>

                                   EXHIBIT A

                                   The Land



Lot 1, Plat 2, GE TECHNOLOGY PARK, as Resubdivision of Parcel B, Quince Orchard
National Geographic Society Property, as shown on plat recorded among the land
records of Montgomery County, Maryland, in Plat Book 193, plats 21040 through
21045.

Saving and excepting that part of Lot 1, Block B, containing 7133 square feet of
land that was conveyed to the State of Maryland by deed dated April 8, 1999 and
recorded among the aforesaid land records in Liber 17015, folio 624

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<PAGE>

                                   EXHIBIT B


                                   The Lease

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