Document:

<PAGE>

                                                                    Exhibit 10.7

                     AMENDMENT NO. 1 TO AGREEMENT OF LEASE
                     -------------------------------------

     THIS AMENDMENT OF LEASE, made as of the ___ day of September, 1998, between
RIVERFRONT OFFICE PARK ASSOCIATES II LIMITED PARTNERSHIP, a Massachusetts
limited partnership (hereinafter referred to as "Landlord") and MAINSPRING
COMMUNICATIONS, INC., a Delaware corporation (hereinafter referred to as
"Tenant").

                               WITNESSETH THAT:

     WHEREAS, Landlord and Tenant are parties to an Agreement of Lease dated as
of July 31, 1996 (said Agreement of Lease being hereinafter referred to as the
"Lease"); and

     WHEREAS, the parties hereto wish to amend the Lease as set forth herein.

     NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged by each of the parties hereto, the
Lease is hereby amended as follows:

     1.  Effective as of December 1, 1998, the 12,293 square feet of rentable
     space on the seventh (7/th/) floor of the Building, as shown on the plan
     attached hereto as Exhibit A and made a part hereof (the "1998 Seventh
                        ---------
     Floor Expansion Space"), shall be added to the Demised Premises for a term
     commencing on such date and ending on November 30, 2002.

     2.  The Term of the Lease is hereby extended from August 14, 2001 until
     November 30, 2002.

     3.  The 1998 Seventh Floor Expansion Space is leased in its present "AS IS"
     condition.

     4.  Effective as of December 1, 1998, Article 1.(18) of the Lease is hereby
     amended to read in its entirety as follows:

         "(18) Yearly Fixed Rent:  For the period from December 1, 1998 through
                                   --------------------------------------------
                                   August 14, 2001: $622,595.43 per annum, based
                                   ---------------
                                   upon a rental rate of (i) $25.47 per square
                                   foot per annum for the 7,069 square feet
                                   initially leased by Tenant under this Lease
                                   and (ii) $36.00 per square foot per annum for
                                   the 1998 Seventh Floor Expansion Space.

                                   For the period from August 15, 2001 through
                                   -------------------------------------------
                                   November 30, 2002:
                                   -----------------

                                           $697,032.00 per annum, based upon a
                                   rental rate of $36.00 per square foot per
                                   annum.
<PAGE>

     5.   Effective as of December 1, 1998, Article, 1.(9) of the Lease is
     hereby amended to read in its entirety as follows:

          "Parking Spaces:    Nineteen (19)."

     6.   Section 3.3 of the Lease is hereby amended to delete therefrom in the
     second sentence thereof the phrase "ninety-five percent (95%)" and to
     insert in substitution thereof the phrase "one hundred percent (100%)".

     7.   Section 3.4 of the Lease is hereby deleted in its entirety.

     8.   Effective as of December 1, 1998, Section 6.4 of the Lease is hereby
     amended to read in its entirety as follows:

          "6.4 Tenant's Proportionate Share.  (a) Tenant's proportionate share
               ----------------------------
          of taxes pursuant to Section 6.2 and operating expenses pursuant to
          Section 6.3, respectively, with respect to the original 7,069 square
          feet of Rentable Area of the Demised Premises shall be 2.17% (7,069
          square feet divided by 326,470 square feet) and 2.20% (7,069 square
          feet divided by 321,917 square feet), respectively.

               (b)  In addition, Tenant's proportionate share of taxes pursuant
          to Section 6.2 with respect to the 1998 Seventh Floor Expansion Space
          shall be 3.77% (12,293 square feet divided by 326,470 square feet) of
          the amount of said taxes imposed against the Building and Land in
          excess of those imposed for the fiscal tax year ending June 30, 1999,
          prorated with respect to any portion of a fiscal tax year in which the
          Term of this Lease ends.

               (c)  In addition, Tenant's proportionate share of operating
          expenses pursuant to Section 6.3 with respect to the 1998 Seventh
          Floor Expansion Space shall be 3.82% (12,293 square feet divided by
          321,917 square feet) of the amount of said operating expenses
          (determined in accordance with the provisions of Section 6.3) incurred
          by Landlord in the operation and maintenance of the Building and the
          Land in excess of those incurred by Landlord for the calendar year
          1998, prorated with respect to any portion of a year in which the Term
          of this Lease ends.

     9.   As used herein all capitalized terms shall have the same meaning as
     used in the Lease, except as otherwise expressly set forth in this
     Amendment. Except as herein modified, the Lease is hereby ratified and
     confirmed in all respects.

                                      -2-
<PAGE>

     IN WITNESS WHEREOF, Landlord and Tenant have caused this instrument to be
executed under seal, all as of the day and year first above written.

                              RIVERFRONT OFFICE PARK ASSOCIATES II LIMITED
                              PARTNERSHIP

                              By:  DARVEL REALTY TRUST
                              Managing General Partner

                              By: /s/ Michael P. Sullivan
                                  -----------------------------------
                                  Michael P. Sullivan, Vice President

                              MAINSPRING COMMUNICATIONS, INC.

                              By: /s/ Mark A. Verdi
                                  ----------------------------------------
                                  Its: Senior Vice President, Finance and
                                       Operations

                                      -3-
<PAGE>

                                                                       Exhibit A
                                                                       ---------

                                  Floor Plan

                                      -4-<PAGE>

                                                                    Exhibit 10.8

                     AMENDMENT NO. 2 TO AGREEMENT OF LEASE
                     -------------------------------------

     THIS AMENDMENT OF LEASE, made as of the 30/th/ day of November, 1998,
between RIVERFRONT OFFICE PARK ASSOCIATES II LIMITED PARTNERSHIP, a
Massachusetts limited partnership (hereinafter referred to as "Landlord") and
MAINSPRING COMMUNICATIONS, INC., a Delaware corporation (hereinafter referred to
as "Tenant").

                               WITNESSETH THAT:

     WHEREAS, Landlord and Tenant are parties to an Agreement of Lease dated as
of July 31, 1996 as amended by Amendment No. 1 to Agreement of Lease dated
September, 1998 ("Amendment No. 1") (said Agreement of Lease, as amended by
Amendment No. 1, being hereinafter referred to as the "Lease"); and

     WHEREAS, the parties hereto wish to further amend the Lease as set forth
herein.

     NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged by each of the parties hereto, the
Lease is hereby amended as follows:

     1.   Effective as of December 1, 1998, the 6,979 square feet of rentable
     space on the seventh (7th) floor of the Building, as shown on the plan
     attached hereto as Exhibit A and made a part hereof (the "Seventh Floor
                        ---------
     Recaptured Space"), shall be eliminated from the Demised Premises for a
     period commencing on such date and ending on November 30, 1999.

     2.   Effective on December 1, 1999, the Seventh Floor Recaptured Space, in
     its then current "AS IS" condition, shall be added to, and again constitute
     a part of, the Demised Premises.

     3.   Effective as of December 1, 1998, Article 1.(18) of the Lease is
     hereby amended to read in its entirety as follows:

          "(18) Yearly Fixed Rent:  (a) For the period from December 1, 1998
                                        ------------------------------------
                                        through November 30, 1999:
                                        -------------------------

                                        $371,351.43 per annum, based upon a
                                        rental rate of (i) $25.47 per square
                                        foot per annum for the 7,069 rentable
                                        square feet constituting that portion of
                                        the Demised Premises initially leased by
                                        Tenant under this Lease and (ii) $36.00
                                        per square foot per annum for the 5,314
                                        rentable square feet constituting that
                                        portion of the 1998 Seventh
<PAGE>

                                      -2-

                                        Floor Expansion Space (as defined in
                                        Amendment No. 1) which is exclusive of
                                        the Seventh Floor Recaptured Space.

                                   (b)  For the period from December 1, 1999
                                        ------------------------------------
                                        through August 14, 2001: $622,595.43 per
                                        -----------------------
                                        annum, based upon a rental rate of (i)
                                        $25.47 per square foot per annum for the
                                        7,069 rentable square feet constituting
                                        that portion of the Demised Premises
                                        initially leased by Tenant under this
                                        Lease and (ii) $36.00 per square foot
                                        per annum for the 12,253 rentable square
                                        feet constituting the 1998 Seventh Floor
                                        Expansion Space.

                                   (c)  For the period from August 15, 2001
                                        -----------------------------------
                                        through November 30, 2002:
                                        -------------------------

                                        $697,032.00 per annum, based upon a
                                        rental rate of $36.00 per square foot
                                        per annum. "

     4.   Effective as of December 1, 1998, Article 1.(9) of the Lease is hereby
     amended to read in its entirety as follows:

          "Parking Spaces:  Twelve (12)."

     5.   Effective as of December 1, 1999, Article 1.(9) of the Lease is hereby
     amended to read in its entirety as follows:

          "Parking Spaces:  Nineteen (19)."

     6.   Effective as of December 1, 1998, Section 6.4 of the Lease is hereby
     amended to read in its entirety as follows:

          "6.4  Tenant's Proportionate Share.  (a)  Tenant's proportionate share
                ----------------------------
          of taxes pursuant to Section 6.2 and operating expenses pursuant to
          Section 6.3, respectively, with respect to the original 7,069 square
          feet of Rentable Area of the Demised Premises shall be 2.17% (7,069
          square feet divided by 326,470 square feet) and 2.20% (7,069 square
          feet divided by 321,917 square feet), respectively.

               (b) In addition, Tenant's proportionate share of taxes pursuant
          to Section 6.2 with respect to that portion of the 1998 Seventh Floor
          Expansion Space which is exclusive of the Seventh Floor Recaptured
          Space shall be 1.63% (5,314 square feet divided by 326,470 square
          feet) of the amount of said taxes imposed against the Building and
          Land in excess of those imposed for the fiscal
<PAGE>

                                      -3-

          tax year ending June 30, 1999, prorated with respect to any portion of
          a fiscal tax year in which the Term of this Lease ends.

               (c) In addition, Tenant's proportionate share of operating
          expenses pursuant to Section 6.3 with respect to that portion of the
          1998 Seventh Floor Expansion Space which is exclusive of the Seventh
          Floor Recaptured Space shall be 1.65% (5,314 square feet divided by
          321,917 square feet) of the amount of said operating expenses
          (determined in accordance with the provisions of Section 6.3) incurred
          by Landlord in the operation and maintenance of the Building and the
          Land in excess of those incurred by Landlord for the calendar year
          1998, prorated with respect to any portion of a year in which the Term
          of this Lease ends.

     7.   Effective as of December 1, 1999, Section 6.4 of the Lease is hereby
     amended to read in its entirety as follows:

          "6.4 Tenant's Proportionate Share.  (a)  Tenant's proportionate share
               ----------------------------
          of taxes pursuant to Section 6.2 and operating expenses pursuant to
          Section 6.3, respectively, with respect to the original 7,069 square
          feet of Rentable Area of the Demised Premises shall be 2.17% (7,069
          square feet divided by 326,470 square feet) and 2.20% (7,069 square
          feet divided by 321,917 square feet), respectively.

               (b)  In addition, Tenant's proportionate share of taxes pursuant
          to Section 6.2 with respect to the 1998 Seventh Floor Expansion Space
          shall be 3.77% (12,293 square feet divided by 326,470 square feet) of
          the amount of said taxes imposed against the Building and Land in
          excess of those imposed for the fiscal tax year ending June 30, 1999,
          prorated with respect to any portion of a fiscal tax year in which the
          Term of this Lease ends.

               (c)  In addition, Tenant's proportionate share of operating
          expenses pursuant to Section 6.3 with respect to the 1998 Seventh
          Floor Expansion Space shall be 3.82% (12,293 square feet divided by
          321,917 square feet) of the amount of said operating expenses
          (determined in accordance with the provisions of Section 6.3) incurred
          by Landlord in the operation and maintenance of the Building and the
          Land in excess of those incurred by Landlord for the calendar year
          1998, prorated with respect to any portion of a year in which the Term
          of this Lease ends.

     8.   As used herein all capitalized terms shall have the same meaning as
     used in the Lease, except as otherwise expressly set forth in this
     Amendment. Except as herein modified, the Lease is hereby ratified and
     confirmed in all respects.
<PAGE>

                                      -4-

     IN WITNESS WHEREOF, Landlord and Tenant have caused this instrument to be
executed under seal, all as of the day and year first above written.

                              RIVERFRONT OFFICE PARK ASSOCIATES II LIMITED
                              PARTNERSHIP

                              By: DARVEL REALTY TRUST
                              Managing General Partner

                              By: /s/ Michael P. Sullivan
                                  -------------------------
                                  Michael P. Sullivan, Vice President

                              MAINSPRING COMMUNICATIONS, INC.

                              By: /s/ Mark A. Verdi (12/22/98)
                                  --------------------------------
                                  Its: Senior Vice President, Finance and
                                       Operations
<PAGE>

                                      -5-

                                                                       Exhibit A
                                                                       ---------

                                  Floor Plan

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