Document:

<PAGE>

CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH
THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE
OMITTED PORTIONS. ASTERISKS DENOTE OMISSIONS.

                                                                   EXHIBIT 10.79

                                                                  EXECUTION COPY

                               @VENTURES III, L.P.

                        AMENDMENT TO MANAGEMENT CONTRACT

     THIS AMENDMENT dated as of June 7, 2002, to the Management Contract dated
as of August 7, 1998 (the "Management Contract"), between @Ventures III, L.P., a
Delaware limited partnership (the "Partnership"), and @Ventures Management, LLC,
a Delaware limited liability company (the "Company"), shall be and become
effective on the Amendment Effective Date (as that term is defined in the
Agreement of Limited Partnership of the Partnership (as amended and in effect
from time to time, the "Agreement").

     For good and valuable consideration, the receipt and sufficiency of which
is hereby acknowledged, the Partnership and the Company hereby agree to amend
the Management Contract as follows:

1.   Amendment to Section 4.  Section 4 of the Management Contract is hereby
     ----------------------
amended by (a) deleting the last sentence thereof, and (b) by adding, at the end
thereof, the following paragraph:

          "Notwithstanding the foregoing or any provision of this Contract to
     the contrary, with respect to all periods from and after February 1, 2002
     through [***], the Company hereby waives [***] management fees; provided
     however, that if, pursuant to Section 11.1(1)(y) of the Agreement, the term
     of the Partnership is extended by the Limited Partners through [***]
     following a termination of @Ventures Expansion Fund, L.P. ("Expansion
     Fund") prior to [***], the Partnership shall pay to the Company a
     management fee equal to the amount of the management fee which would have
     been payable by Expansion Fund to @Ventures Expansion Management LLC for
     the period between the date of the termination of Expansion Fund and [***]
     (i.e., fees at an annualized rate of $[***], but reduced by amounts paid by
     Expansion Fund on account of periods preceding the date of termination of
     the Expansion Fund), any such fee to be payable in advance, in a lump sum,
     at the time specified in Section 11.1(1)(y) of the Agreement. If, pursuant
     to Section 11.1(1)(x) of the Agreement, the term of the Partnership is
     extended, the management fee for any such extension period payable to the
     Company shall be an amount mutually acceptable to the Company and the
     Partnership (any such Partnership approval to require the consent of
     Two-Thirds in Interest of the Limited Partners), but in no event shall such
     fees exceed $[***] per year, and any such management fee shall be payable
     in semi-annual installments on January 1 and July 1 of each year during the
     extension period."

2.   Amendment to Section 5.  Section 5 of the Management Contract is hereby
     ----------------------
amended by adding, at the end thereof, the following sentence:

<PAGE>

     "Notwithstanding the foregoing, any amount which, pursuant to this Section
     5, is to be retained by the Company and credited against the management fee
     payable by the Partnership in respect of any period from and after the
     Amendment Effective Date through [***], shall, if the Partnership is not at
     the time paying a management fee equal to or greater than such amount,
     instead be paid to the Partnership."

3.   Amendment to Section 6.  Section 6 of the Management Contract is hereby
     ----------------------
amended by adding, at the end thereof, the following sentence:

     "Notwithstanding any provision of the Agreement or this Contract to the
     contrary, this Contract shall automatically terminate on the last day of
     the Partnership term determined in accordance with Section 2.5 of the
     Agreement."

                            [Signature page follows.]

                                      - 2 -

<PAGE>

          IN WITNESS WHEREOF, the Partnership and the Company have caused this
     Amendment be signed (in counterparts) as of the date first above written.

                                        @VENTURES III, L.P.

                                        By:  @Ventures Partners III, LLC,
                                             its general partner

                                        By: /s/ Peter H. Mills
                                            ---------------------

                                        Name: Peter H. Mills
                                              --------------------------
                                              Authorized Managing Member

                                        @VENTURES MANAGEMENT, LLC

                                        By: /s/ Peter H. Mills
                                            ------------------

                                        Name: /s/ Peter H. Mills
                                              ------------------
                                              Authorized Member

                                      - 3 -<PAGE>

CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN OMITTED AND FILED SEPARATELY WITH
THE COMMISSION. CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH RESPECT TO THE
OMITTED PORTIONS. ASTERISKS DENOTE OMISSIONS.

                                                                   EXHIBIT 10.80

                                                                  EXECUTION COPY

                                AMENDMENT TO THE
                             MANAGEMENT CONTRACT OF
                        @VENTURES FOREIGN FUND III, L.P.

     This Amendment (this "Amendment"), dated as of June 7, 2002, to Management
Contract of @Ventures Foreign Fund III, L.P. dated as of December 22, 1998 (as
amended to date, the "Contract") between @Ventures Foreign Fund III, L.P., a
Delaware limited partnership (the "Partnership"), and @Ventures Management, LLC,
a Delaware limited liability company (the "Company"). Capitalized terms used
herein but not otherwise defined herein shall have the respective meanings
ascribed to them in the Contract.

     WHEREAS, the Company has executed Amendment No. 2 to the Agreement of
Limited Partnership of @Ventures Foreign Fund III, L.P. dated the same date
hereof (together with the Agreement of Limited Partnership of the Partnership
dated December 22, 1998, as amended to date, the "Agreement"), pursuant to which
the Company has agreed to waive [***] management fees and other amounts payable
under the Agreement in respect from February 1, 2002 through [***]; and

     WHEREAS, the Partnership and the Company desire to effect such waiver of
the management fees and other amounts payable under the Contract by amending the
Contract through this Amendment.

     NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the undersigned parties hereby
agree as follows:

1.   Amendments to Section 4 of Contract. Section 4 of the Contract is hereby
amended by (a) in the first sentence, deleting the phrase "four (4) years after
the Initial Closing Date" and substituting in its place the phrase "[***]", (b)
deleting the last two sentences thereof, and (c) by adding, at the end thereof,
the following paragraph:

     "Notwithstanding any provision of this Contract to the contrary, with
     respect to all periods from and after February 1, 2002 through [***], [***]
     management fees or other amounts shall be payable by the Partnership (or
     any of its limited partners) to the Company. If, pursuant to Section
     11.1(1) of the Agreement, the term of the Partnership is extended, the
     management fee for any such extension period payable to the Company shall
     be an amount mutually acceptable to the Company and the Partnership (any
     such Partnership approval shall require the consent of the Majority in
     Interest of Limited Partners of the Partnership), but in no event shall
     such fees exceed $[***] per year, and any such management fee shall be
     payable in semi-annual installments on January 1 and July 1 of each year
     during the extension period."

<PAGE>

2.   Amendments to Section 5 of Contract.  Section 5 of the Contract is hereby
     -----------------------------------
amended by adding at the end thereof, the following sentence:

     "Notwithstanding the foregoing, any amount which is to be retained by the
     Company under Section 5 of this Contract and credited against the
     management fee payable by the Partnership in respect of any period after
     the date hereof, shall instead be paid to the Partnership."

3.   Amendments to Section 6 of Contract.  Section 6 of the Contract is hereby
     -----------------------------------
amended by adding at the end thereof, the following sentence:

     "Notwithstanding any provision of this Contract, this Contract shall
     automatically terminate on the last day of the Partnership term determined
     in accordance with Section 2.5 of the Agreement."

4.   Legal Fees.  All of the legal, accounting and other fees and expenses
     ----------
relating to this Amendment shall be paid exclusively by the Company.

5.   Ratification.  In all other respects, the Contract is hereby ratified and
     ------------
confirmed and shall remain in full force and effect.

6.   Counterparts.  This Amendment may be executed in two or more counterparts,
     ------------
each of which shall be deemed an original and all of which together shall
constitute one and the same instrument.

                            [Signature pages follow.]

                                      - 2 -

<PAGE>

     IN WITNESS WHEREOF, the parties have duly executed this Amendment as of the
date first above written.

                                        COMPANY:

                                        @VENTURES MANAGEMENT, LLC

                                        By: /s/ Peter H. Mills
                                            ----------------------------------
                                            Authorized Managing Member

                                        PARTNERSHIP:

                                        @VENTURES FOREIGN FUND III, L.P.

                                        By   @Ventures Partners III, LLC, its
                                             General Partner

                                             By /s/ Peter H. Mills
                                               --------------------------------

                                             Name Peter Mills
                                                  -----------

                                             Title Authorized Member
                                                   -----------------

                                      - 3 -

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