<PAGE>

                                                                    Exhibit 10.1

                               AMENDMENT NO. 1 TO
                          CREDIT AND GUARANTY AGREEMENT

     THIS AMENDMENT NO. 1 TO CREDIT AND GUARANTY AGREEMENT, dated as of June 2,
2006 (this "AMENDMENT"), by and among NaviSite, Inc., a Delaware corporation
("COMPANY"), the Subsidiaries of the Company party hereto, as Guarantors
("GUARANTORS"), the Lenders (defined below) party hereto and Silver Point
Finance, LLC ("SILVER POINT"), as Administrative Agent ("ADMINISTRATIVE AGENT").

                                    RECITALS:

     WHEREAS, the Company, the Guarantors, the lenders party thereto (the
"LENDERS"), the Administrative Agent and Silver Point, as Collateral Agent are
parties to that certain Credit and Guaranty Agreement dated as of April 11, 2006
(the "CREDIT AGREEMENT"; capitalized terms used and not defined herein shall
have the meanings set forth in the Credit Agreement); and

     WHEREAS, the Company has requested that the Lenders agree to amend the
Credit Agreement as set forth below, and the Lenders have agreed to amend the
Credit Agreement subject to the terms and conditions set forth herein, the
Guarantors, the Lenders, and the Agents now desire to amend the Credit Agreement
in certain respects, as hereinafter provided;

     NOW, THEREFORE, in consideration of the premises set forth above, the terms
and conditions contained herein and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree as follows:

     Section 1 Amendment.

          Section 6.8(a) of the Credit Agreement is hereby amended and restated
in its entirety as set forth below:

               (a) Fixed Charge Coverage Ratio. Company shall not permit the
     Fixed Charge Coverage Ratio as of the last day of any Fiscal Quarter,
     beginning with the Fiscal Quarter ending April 30, 2006, to be less than
     the correlative ratio indicated:

<TABLE>
<CAPTION>
                          FIXED CHARGE
FISCAL QUARTER ENDING:   COVERAGE RATIO
----------------------   --------------
<S>                      <C>
April 30, 2006              0.80:1.00
July 31, 2006               1.05:1:00
October 31, 2006            1.15:1.00
January 1, 2007             1.25:1.00
April 30, 2007              1.40:1.00
</TABLE>

<PAGE>

<TABLE>
<CAPTION>
                          FIXED CHARGE
FISCAL QUARTER ENDING:   COVERAGE RATIO
----------------------   --------------
<S>                      <C>
July 31, 2007               1.35:1.00
October 31, 2007            1.25:1.00
January 31, 2008            1.20:1.00
Between (and
   including)
   April 30, 2008 and
   October 31, 2008         1.15:1.00
Between (and
   including)
   January 31, 2009
   and April 30, 2010       1.20:1.00
On July 31, 2010
   and thereafter           1.25:1.00
</TABLE>

     Section 2 Conditions to Effectiveness of this Amendment.

          This Amendment shall be effective as of the date hereof, upon the
satisfaction (or waiver) of the following conditions precedent:

               (a) the Administrative Agent shall have received counterparts to
     this Amendment duly executed and delivered by the Company, each Guarantor
     and the Requisite Lenders;

               (b) the Company shall have paid all costs, fees and expenses
     incurred by the Administrative Agent in connection with the preparation of
     this Amendment;

               (c) no Default or Event of Default shall have occurred and be
     continuing or shall result from the execution and delivery of this
     Amendment; and

               (d) the representations and warranties contained herein and in
     the Credit Documents shall be true and correct in all material respects on
     and as of the date hereof to the same extent as though made on and as of
     such date, except to the extent such representations and warranties
     specifically relate to an earlier date, in which case such representations
     and warranties shall have been true and correct in all material respects on
     and as of such earlier date.

     Section 3 Representations and Warranties.

          The Company and each Guarantor hereby represent and warrant to each
Lender, the Administrative Agent and the Collateral Agent that (a) it is duly
organized, validly existing and in good standing under the laws of its
jurisdiction of organization, (b) it has all requisite power and authority to
enter into is Amendment, (c) the execution,


                                        2

<PAGE>

delivery and performance by it of this Amendment (i) has been duly authorized by
all necessary organizational action and (ii) does not and will not (A) violate
any provision of any law or any governmental rule or regulation applicable to it
or any of the Organizational Documents; (B) conflict with, result in a breach of
or constitute (with due notice or lapse of time or both) a default under any
Contractual Obligation binding on it or (C) result in or require the creation or
imposition of any Lien upon any of its properties or assets and (d) this
Amendment has been duly executed and delivered by it and is its legally valid
and binding obligation, enforceable against it in accordance with its terms,
except as may be limited by bankruptcy, insolvency, reorganization, moratorium
or similar laws relating to or limiting creditors' rights generally or by
equitable principles relating to enforceability.

     Section 4 Miscellaneous.

               (a) The amendments set forth herein is effective solely for the
     purposes set forth herein and shall be limited precisely as written, and
     shall not be deemed to (i) be a consent to, or acknowledgment of, any
     amendment, waiver or modification of any other term or condition of the
     Credit Agreement or of any other Credit Document or (ii) prejudice any
     right or remedy which the Administrative Agent, the Collateral Agent or any
     Lender may now have or may have in the future under or in connection with
     the Credit Agreement as amended hereby or any other Credit Document. This
     Amendment shall be construed in connection with and as part of the Credit
     Agreement, and all terms, conditions, representations, warranties,
     covenants and agreements set forth in the Credit Agreement, each other
     Credit Document and each other instrument or agreement referred to therein,
     except as herein amended, are hereby ratified and confirmed and shall
     remain in full force and effect.

               (b) Nothing contained in this Amendment shall extinguish the
     obligations for the payment of money outstanding under the Credit Agreement
     or discharge or release the Liens created under or affect the priority of
     any Collateral Document.

               (c) This Amendment may be executed in any number of counterparts
     and by different parties hereto in separate counterparts, each of which
     shall be deemed to be an original, but all of which taken together shall
     constitute one and the same agreement. Delivery of an executed counterpart
     of this Amendment by telefacsimile or a .PDF by electronic mail shall be
     equally as effective as delivery of an original executed counterpart of
     this Amendment. Any party delivering an executed counterpart of this
     Amendment by telefacsimile also shall deliver an original executed
     counterpart of this Amendment but the failure to deliver an original
     executed counterpart shall not affect the validity, enforceability, and
     binding effect of this Amendment.

               (d) Any provision of this Amendment which is prohibited or
     unenforceable in any jurisdiction shall, as to such jurisdiction, be
     ineffective to the extent of such prohibition or unenforceability without
     invalidating the


                                        3

<PAGE>

     remaining portions hereof or affecting the validity or enforceability of
     such provision in any other jurisdiction.

               (e) THIS AMENDMENT AND THE RIGHTS AND OBLIGATIONS OF THE PARTIES
     HEREUNDER SHALL BE GOVERNED BY, AND SHALL BE CONSTRUED AND ENFORCED IN
     ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD TO
     CONFLICT OF LAWS PRINCIPLES (OTHER THAN SECTIONS 5-1401 AND 5-1402 OF THE
     NEW YORK GENERAL OBLIGATIONS LAW) THEREOF.

               (f) Each of the parties hereto agrees that no party hereto shall
     be deemed to be the drafter of this Amendment.

               (g) EACH GUARANTOR HEREBY CONSENTS TO THIS AMENDMENT AND HEREBY
     CONFIRMS AND AGREES THAT (A) NOTWITHSTANDING THE EFFECTIVENESS OF THIS
     AMENDMENT, ITS OBLIGATIONS UNDER SECTION 7 OF THE CREDIT AGREEMENT AND THE
     OTHER CREDIT DOCUMENT ARE, AND SHALL CONTINUE TO BE, IN FULL FORCE AND
     EFFECT AND ARE HEREBY RATIFIED AND CONFIRMED IN ALL RESPECTS AND (B) THE
     COLLATERAL DOCUMENTS TO WHICH IT IS A PARTY AND ALL OF THE COLLATERAL
     DESCRIBED THEREIN DO, AND SHALL CONTINUE TO, SECURE THE PAYMENT OF ALL OF
     THE OBLIGATIONS SECURED THEREBY.

                            (Signature Page Follows)


                                        4

<PAGE>

          IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be executed by their respective officers thereunto duly authorized, as of the
date first above written.

                                        Company:

                                        NAVISITE, INC.


                                        By: /s/ John J. Gavin Jr.
                                            ------------------------------------
                                        Name: John J. Gavin Jr.
                                        Title: CFO and Treasurer

                                                                 Amendment No. 1
                                                to Credit and Guaranty Agreement

<PAGE>

                                        Guarantors:

                                        AVASTA, INC.
                                        CLEARBLUE TECHNOLOGIES MANAGEMENT, INC.
                                        CLEARBLUE TECHNOLOGIES/
                                           CHICAGO-WELLS, INC.
                                        CLEARBLUE TECHNOLOGIES/ LAS VEGAS, INC.
                                        CLEARBLUE TECHNOLOGIES/
                                           LOS ANGELES, INC.
                                        CLEARBLUE TECHNOLOGIES/ MILWAUKEE, INC.
                                        CLEARBLUE TECHNOLOGIES/ OAK BROOK, INC.
                                        CLEARBLUE TECHNOLOGIES/ VIENNA, INC.
                                        CLEARBLUE TECHNOLOGIES/ DALLAS, INC.
                                        CLEARBLUE TECHNOLOGIES/ NEW YORK, INC.
                                        CLEARBLUE TECHNOLOGIES/ SAN
                                           FRANCISCO, INC.
                                        CLEARBLUE TECHNOLOGIES/
                                           SANTA CLARA, INC.
                                        CONXION CORPORATION
                                        INTREPID ACQUISITION CORP.
                                        LEXINGTON ACQUISITION CORP.
                                        MANAGEDOPS.COM, INC.
                                        SUREBRIDGE ACQUISITION CORP.
                                        SUREBRIDGE SERVICES, INC.
                                        SITEROCK CORPORATION
                                        NAVISITE ACQUISITION SUBSIDIARY, INC.
                                        CLICKHEAR, INC.


                                        By: /s/ John J. Gavin Jr.
                                            ------------------------------------
                                        Name: John J. Gavin Jr.
                                        Title: CFO and Treasurer

                                                                 Amendment No. 1
                                                to Credit and Guaranty Agreement

<PAGE>

                                        SILVER POINT FINANCE, LLC,
                                        as Administrative Agent and Collateral
                                        Agent


                                        By: /s/ Richard Petrilli
                                            ------------------------------------
                                        Name: Richard Petrilli
                                        Title: Authorized Signatory

                                                                 Amendment No. 1
                                                to Credit and Guaranty Agreement

<PAGE>

                                        SPF CDO I, LLC,
                                        as a Lender


                                        By: /s/ Richard Petrilli
                                            ------------------------------------
                                        Name: Richard Petrilli
                                        Title: Authorized Signatory

                                                                 Amendment No. 1
                                                to Credit and Guaranty Agreement

<PAGE>

                                        FIELD POINT III, LTD.,
                                        as a Lender


                                        By: /s/ Richard Petrilli
                                            ------------------------------------
                                        Name: Richard Petrilli
                                        Title: Authorized Signatory

                                                                 Amendment No. 1
                                                to Credit and Guaranty Agreement

<PAGE>

                                        FIELD POINT I, LTD.,
                                        as a Lender


                                        By: /s/ Richard Petrilli
                                            ------------------------------------
                                        Name: Richard Petrilli
                                        Title: Authorized Signatory

                                                                 Amendment No. 1
                                                to Credit and Guaranty Agreement