<PAGE>
                                                                   EXHIBIT 10.31

NEITHER THIS WARRANT NOR THE SHARES OF STOCK ISSUABLE UPON EXERCISE HEREOF HAVE
BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED. NO SALE, TRANSFER
OR OTHER DISPOSITION OF THIS WARRANT OR SAID SHARES MAY BE EFFECTED WITHOUT (i)
AN EFFECTIVE REGISTRATION STATEMENT RELATED THERETO, OR (ii) AN OPINION OF
COUNSEL, REASONABLY SATISFACTORY TO COUNSEL TO THE COMPANY, THAT AN EXEMPTION
FROM REGISTRATION UNDER SAID ACT IS AVAILABLE.

March 29, 2002                STOCK PURCHASE WARRANT             Warrant No.: __


              To Subscribe for and Purchase Class A Common Stock of


                            NEXTERA ENTERPRISES, INC.

        THIS CERTIFIES that, for value received, Fleet National Bank (together
with any subsequent transferees of all or any portion of this Warrant, the
"Holder"), is entitled, upon the terms and subject to the conditions hereinafter
set forth, to subscribe for and purchase from Nextera Enterprises, Inc., a
Delaware corporation (hereinafter called the "Company"), up to one hundred
eighty-one thousand, eight hundred and eighteen (181,818) fully paid and
non-assessable shares of the Company's Class A Common Stock, $0.001 par value
per share (the "Shares"), at the price equal to the Exercise Price (as defined
in Section 1 hereof) (subject to adjustment as provided in Section 7 hereof).
The number and character of such Shares are subject to adjustment as provided
herein. Capitalized terms not otherwise defined herein shall have the meanings
given in that certain Amended and Restated Credit Agreement dated March 29,
2002, by and among the Company and the Holder, as agent, and other instruments,
agreements and documents, providing, subject to the terms and conditions
thereof, for loans and other credit accommodations to be made by the Holder and
the lenders named therein to the Company (as the same may be amended, modified,
changed, extended or renewed from time to time, collectively, the "Credit
Documents").

        1. Definitions. As used herein the following terms shall have the
following meanings:

                "Act" means the Securities Act of 1933 as amended, or a similar
                Federal statute and the rules and regulations of the Commission
                issued under that Act, as they each may, from time to time, be
                in effect.

                "Additional Shares of Common Stock" shall mean all shares of
                Common Stock issued (or, pursuant to Section 7(c), deemed to be
                issued) by the Company after the Original Issue Date, but shall
                not include:

                (A) shares of Common Stock issued or issuable upon conversion of
                shares of all of preferred stock of the Company outstanding as
                of the Original Issue Date;

                (B) shares of Common Stock issued or issuable upon exercise of
                this Warrant or any other warrant or option of the Company
                outstanding as of the Original Issue Date;

                (C) shares of Common Stock issued by way of dividend or other
                distribution on shares of Common Stock excluded from the
                definition of Additional Shares of Common Stock by the foregoing
                clause (A) or (B) or on Common Stock so excluded; or

                (D) shares issued under an employee stock purchase plan or
                pursuant to options exercisable for shares of Common Stock (such
                number subject to equitable adjustment in the event of any stock
                dividend, stock split, combination, reorganization,
                recapitalization, reclassification or other similar event),
                issued after the date of this Warrant to directors, officers,
                employees or consultants of the Company and any Subsidiary
                pursuant to any qualified or non-qualified stock option plan or
                other equity incentive plan approved by the Board of Directors
                of the Company, equal to the first 30% of the outstanding stock
                of the Company, calculated on a post-Original Issue Date,
                fully-diluted basis.


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                "Common Stock" shall mean the Class A Common Stock of the
                Company, $0.001 par value per share.

                "Convertible Securities" shall mean any evidences of
                indebtedness, shares or other securities directly or indirectly
                convertible into or exchangeable for Common Stock.

                "Exercise Price" shall mean $0.60 per share.

                "New Financing Source" shall mean a source other than the
                Company.

                "Option" shall mean rights, options or warrants to subscribe
                for, purchase or otherwise acquire Common Stock or Convertible
                Securities.

                "Original Issue Date" shall mean the date on which this Warrant
                is originally issued.

        2. Purchase Rights. The purchase rights represented by this Warrant are
exercisable by the Holder in whole or in part (and not as to a fractional
share), at any time and from time to time commencing on the date hereof and
ending at 5:00 p.m. on the date (the "Expiration Date") eighteen (18) months
after the indefeasible payment in full in cash or cash equivalents of the Credit
Obligations.

        3. Exercise of Warrant; Net Issue Exercise.

        3.1 Exercise of Warrant. Subject to Section 2 above, the purchase rights
represented by this Warrant may be exercised, in whole or in part and from time
to time, by the surrender of this Warrant and the duly executed Notice of
Exercise (the form of which is attached as Exhibit A) at the principal office of
the Company and by the payment to the Company, by check, of an amount equal to
the then applicable Exercise Price per share multiplied by the number of Shares
then being purchased. Upon exercise, the Holder shall be entitled to receive,
within a reasonable time, a certificate or certificates, issued in the Holder's
name or in such name or names as the Holder may direct, for the number of Shares
so purchased. The Shares so purchased shall be deemed to be issued as of the
close of business on the date on which this Warrant shall have been exercised.

        3.2. Net Issue Exercise.

               (a) In lieu of exercising this Warrant as set forth in Section
        3.1, the Holder may elect to receive Shares equal to the value of this
        Warrant (or the portion thereof being cancelled) by surrender of this
        Warrant at the principal office of the Company together with notice of
        such election in which event the Company shall issue to the Holder a
        number of Shares computed using the following formula:

                                  X = Y (A - B)
                                      ---------
                                          A

Where   X =     the number of Shares to be issued to the Holder;

        Y =     the number of Shares purchasable under this Warrant, or if only
                a portion of this Warrant is being cancelled, the gross number
                of Shares covered by the portion of this Warrant being
                cancelled;

        A =     the fair market value of one Share, as determined by the Board
                of Directors of the Company pursuant to paragraph (b) below, as
                at the time the net issue election is made pursuant to this
                Section (the "Determination Date"); and

        B =     the Exercise Price (as adjusted to the date of such
                calculations).

Such Shares shall be issued as soon as practicable after the Determination Date.

               (b) For purposes of this Section, fair market value of a Share
        shall be determined as follows:

                               (A) If the Company's Common Stock is not publicly
                       traded at the Determination Date, the fair market value
                       of a Share shall be a value reasonably


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                        determined by the Company's Board of Directors. In the
                        event that the Holder disagrees with the Board of
                        Directors' determination of fair market value, then the
                        fair market value shall be determined by an appraiser
                        selected by the Holder (the "Holder's Appraiser") and
                        whose appraisal (the "Holder's Appraisal") shall be
                        furnished to the Company within 20 days after the Board
                        of Directors' determination of fair value, and if the
                        Company does not object to such determination within 15
                        days after receipt of the Holder's appraisal, then the
                        fair market value determined by the Holder's Appraiser
                        shall be the fair market value of a Share. In the event
                        that the Company objects to such determination then the
                        Company shall select an appraiser (the "Company's
                        Appraiser") who shall review the determination of the
                        Holder's Appraiser and issue a report thereon (the
                        "Company's Appraisal") within 30 days after the delivery
                        of the Holder's Appraisal to the Company and within 10
                        days after the issuance of such report to the Holder's
                        Appraiser, the Holder's Appraiser and the Company's
                        Appraiser shall meet to negotiate in good faith to reach
                        agreement on the fair market value of a Share, and such
                        agreed value shall be the fair market value of a Share.
                        In the event that the Company's Appraiser and the
                        Holder's Appraiser are unable to reach agreement then
                        such Appraisers shall select an appraiser (the "Third
                        Appraiser") within 5 days after the meeting between the
                        Holder's Appraiser and the Company's Appraiser, and the
                        average of two appraisals, consisting of the appraisal
                        made by the Third Appraiser and the appraisal of the
                        Holder's Appraiser and Company's Appraiser (whichever is
                        closest to that of the Third Appraiser), shall be
                        conclusive and binding on the Company and the Holder.
                        The Company and the Holder shall each pay one half (1/2)
                        of the fees and expenses of each of the Company's
                        Appraiser, the Holder's Appraiser and the Third
                        Appraiser.

                               (B) if the Company's Common Stock is publicly
                       traded on the Determination Date, the fair market value
                       of a Share shall be equal to (1) the average of the
                       closing prices quoted on the Nasdaq Stock Exchange, Inc.,
                       if applicable, or the average of the last bid and asked
                       prices of the Common Stock quoted in the Nasdaq OTC
                       Bulletin Board or the over-the-counter-market, or (2) if
                       the Common Stock is then traded on a national securities
                       exchange, the average of the high and low closing prices
                       of the Common Stock listed on the principal national
                       securities exchange on which the Common Stock is so
                       traded, in each case for the twenty (20) trading days
                       preceding the Determination Date.

        4. Shares to be Issued; Reservation of Shares. The Company covenants
that the Shares that may be issued upon the exercise of the purchase rights
represented by this Warrant will, upon issuance, be fully paid and
non-assessable, and free from all liens and charges with respect to the issue
thereof. During the period within which the purchase rights represented by the
Warrant may be exercised, the Company will at all times have authorized and
reserved, for the purpose of issuance upon exercise of the purchase rights
represented by this Warrant, a sufficient number of shares of its Common Stock
to provide for the exercise of the right represented by this Warrant.

        5. No Fractional Shares. No fractional shares shall be issued upon the
exercise of this Warrant. In lieu thereof, a cash payment shall be made equal to
such fraction multiplied by the fair market value of such shares of Common
Stock, as determined pursuant to Section 3.2(b) above.

        6. Adjustment for Merger, Consolidation or Sale of Assets. In the event
that at any time or from time to time after the Original Issue Date, the Company
shall merge or consolidate with or into another entity or sell all or
substantially all of its assets, the Holder hereof shall thereafter have the
right to receive the kind and amount of shares of stock, other securities,
property or cash deliverable or payable to the holders of the Common Stock of
the Company that the Holder hereof upon exercise of this Warrant would have been
entitled to had the Holder hereof exercised the remaining portion of this
Warrant into shares of Common Stock immediately prior thereto.

        7. Adjustment of Exercise Price and Number of Shares.


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               (a) Adjustment of Exercise Price and Number of Shares. The
        Exercise Price and number of shares of Common Stock issuable upon the
        exercise of the Warrant shall be adjusted as set forth in this Section 7
        with the intent that the rights of the Holder to exercise shall not be
        impaired.

               (b) Adjustment for Combination, Consolidation, Stock Dividend or
        Subdivision of Common Stock. If the outstanding shares of Common Stock
        shall be subdivided into a greater number of shares or a dividend in
        Common Stock shall be paid in respect of Common Stock, the Exercise
        Price in effect immediately prior to such subdivision or at the record
        date of such dividend shall simultaneously with the effectiveness of
        such subdivision or immediately after the record date of such dividend
        be proportionately reduced. If outstanding shares of Common Stock shall
        be combined or consolidated into a smaller number of shares, the
        Exercise Price in effect immediately prior to such combination or
        consolidation shall, simultaneously with the effectiveness of such
        combination or consolidation, be proportionately increased. When any
        adjustment is required to be made in the Exercise Price, the number of
        shares of Common Stock purchasable upon the exercise of this Warrant
        shall be changed to the number determined by dividing (i) an amount
        equal to the number of shares issuable upon the exercise of this Warrant
        immediately prior to such adjustment, multiplied by the Exercise Price
        in effect immediately prior to such adjustment, by (ii) the Exercise
        Price in effect immediately after such adjustment.

               (c) Issue of Options and Convertible Securities Deemed Issue of
        Additional Shares of Common Stock. If the Company at any time or from
        time to time after the Original Issue Date shall issue any Options or
        Convertible Securities or shall fix a record date for the determination
        of holders of any class of securities entitled to receive any such
        Options or Convertible Securities, then the maximum number of shares of
        Common Stock (as set forth in the instrument relating thereto, without
        regard to any provision contained therein for a subsequent adjustment of
        such number) issuable upon the exercise of such Options or, in the case
        of Convertible Securities or Options therefor, the conversion or
        exchange of such Convertible Securities, shall be deemed to be
        Additional Shares of Common Stock issued as of the time of such issue
        or, in case such a record date shall have been fixed, as of the close of
        business on such record date, provided that Additional Shares of Common
        Stock shall not be deemed to have been issued unless the consideration
        per share (determined pursuant to paragraph (e) below) of such
        Additional Shares of Common Stock would be less than the Exercise Price
        in effect on the date of and immediately prior to such issue, or such
        record date, as the case may be, and provided further in any such case
        in which Additional Shares of Common Stock are deemed to be issued:

                       (i) No further adjustment in the Exercise Price shall be
               made upon the subsequent issue of Convertible Securities or
               shares of Common Stock upon the exercise of such Options or
               conversion or exchange of such Convertible Securities;

                       (ii) If such Options or Convertible Securities by their
               terms provide, with the passage of time or otherwise, for any
               increase in the consideration payable to the Company, or decrease
               in the number of shares of Common Stock issuable, upon the
               exercise, conversion or exchange thereof, the Exercise Price
               computed upon the original issue thereof (or upon the occurrence
               of a record date with respect thereto), and any subsequent
               adjustments based thereon, shall, upon any such increase or
               decrease becoming effective, be recomputed to reflect such
               increase or decrease insofar as it affects such Options or the
               rights of conversion or exchange under such Convertible
               Securities;

                       (iii) No readjustment pursuant to clause (ii) above shall
               have the effect of increasing the Exercise Price to an amount
               which exceeds the lower of (A) the Exercise Price immediately
               prior to the adjustment affected upon the original issue of
               Options or Convertible Securities (or upon the occurrence of a
               record date with respect thereto) pursuant to the provisions
               hereof, or (B) the Exercise Price that would have resulted from
               any issuance of Additional Shares of Common Stock between the
               original adjustment date and such readjustment date;

                       (iv) Upon the expiration or termination of any
               unexercised Option, the Exercise Price shall be readjusted to the
               Exercise Price which would have been in effect


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               at the time of such expiration or termination had such Option
               never been issued (but including the recalculation of any
               intervening adjustments), and the Additional Shares of Common
               Stock deemed issued as the result of the original issue of such
               Option shall not be deemed issued for the purposes of any
               subsequent adjustment of the Exercise Price; and

                       (v) In the event of any change in the number of shares of
               Common Stock issuable upon the exercise, conversion or exchange
               of any Option or Convertible Security, including, but not limited
               to, a change resulting from the antidilution provisions thereof,
               the Exercise Price then in effect shall forthwith be readjusted
               to such Exercise Price as would have obtained had the adjustment
               which was made upon the issuance of such Option or Convertible
               Security (prior to such change) been made upon the basis of such
               change, but no further adjustment shall be made for the actual
               issuance of Common Stock upon the exercise or conversion of any
               such Option or Convertible Security.

               (d) Adjustment of Exercise Price Upon Issuance of Additional
        Shares of Common Stock. In the event the Company shall at any time after
        the Original Issue Date issue Additional Shares of Common Stock
        (including Additional Shares of Common Stock deemed to be issued
        pursuant to paragraph (c) above), without consideration or for a
        consideration per share less than the Exercise Price in effect on the
        date of and immediately prior to such issue, then and in such event,
        such Exercise Price shall be reduced, concurrently with such issue, to a
        price (calculated to the nearest cent) calculated as follows:

                       (i) The adjusted Exercise Price shall be equal to a
               fraction: (A) the numerator of which shall be the number of
               shares of Common Stock outstanding immediately prior to such
               issue (including shares described in clause (ii) below), plus the
               number of shares of Common Stock which the aggregate
               consideration received by the Company for the total number of
               Additional Shares of Common Stock so issued would purchase at
               such Exercise Price; and (B) the denominator of which shall be
               the number of shares of Common Stock outstanding immediately
               prior to such issue (including shares described in clause (ii)
               below) plus the number of such Additional Shares of Common Stock
               so issued.

                       (ii) For the purposes of clause (i), the number of shares
               of Common Stock outstanding immediately prior to such issue shall
               be calculated on a fully diluted basis, as if all Convertible
               Securities had been fully converted into shares of Common Stock
               immediately prior to such issuance and the Warrant and any other
               outstanding Options had been fully exercised immediately prior to
               such issuance (and any resulting Convertible Securities fully
               converted into Common Stock) as of such date.

                       (iii) The applicable Exercise Price shall not be reduced
               at the time of any issuance of Additional Shares of Common Stock
               if the amount of such reduction would be an amount less than
               $0.01, but any such amount shall be carried forward and reduction
               with respect thereto shall be made at the time and together with
               any subsequent reduction which, together with such amount and any
               other amounts so carried forward, shall aggregate $0.01 or more.

               (e) Determination of Consideration. For purposes of paragraph
        (d), the consideration received by the Company for the issue of any
        Additional Shares of Common Stock shall be computed as follows:

                       (i) Cash and Property: Such consideration shall:

                               (A) insofar as it consists of cash, be computed
                       at the aggregate of cash received by the Company;

                               (B) insofar as it consists of property other than
                       cash, be computed at the fair market value thereof at the
                       time of such issue, as determined in good faith by the
                       Board of Directors; and


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                               (C) in the event Additional Shares of Common
                       Stock are issued together with other shares or securities
                       or other assets of the Company for consideration which
                       covers both, be the proportion of such consideration so
                       received, computed as provided in clauses (A) and (B)
                       above, as determined in good faith by the Board of
                       Directors.

                       (ii) Options and Convertible Securities. The
               consideration per share received by the Company for Additional
               Shares of Common Stock deemed to have been issued pursuant to
               paragraph (c), relating to Options and Convertible Securities,
               shall be determined by dividing:

                               (A) the total amount, if any, received or
                       receivable by the Company as consideration for the issue
                       of such Options or Convertible Securities, plus the
                       minimum aggregate amount of additional consideration (as
                       set forth in the instruments relating thereto, without
                       regard to any provision contained therein for a
                       subsequent adjustment of such consideration) payable to
                       the Company upon the exercise of such Options or the
                       conversion or exchange of such Convertible Securities, or
                       in the case of Options for Convertible Securities, the
                       exercise of such Options for Convertible Securities and
                       the conversion or exchange of such Convertible
                       Securities; by

                               (B) the maximum number of shares of Common Stock
                       (as set forth in the instrument relating thereto, without
                       regard to any provision contained therein for a
                       subsequent adjustment of such number) issuable upon the
                       exercise of such Options or the conversion or exchange of
                       such Convertible Securities.

               (f) Certificate as to Adjustments. Upon the occurrence of each
        adjustment or readjustment of the Exercise Price pursuant to this
        Section 7, the Company at its expense shall promptly compute such
        adjustment or readjustment in accordance with the terms hereof and
        furnish to the Holder a certificate setting forth such adjustment or
        readjustment and showing in detail the facts upon which such adjustment
        or readjustment is based. The Company shall, upon the written request at
        any time of the Holder, furnish or cause to be furnished to such holder
        a like certificate setting forth (i) such adjustments and readjustments,
        (ii) the Exercise Price at the time in effect, and (iii) the number of
        shares of Common Stock and the amount, if any, of other property which
        at the time would be received upon the exercise of the Warrant.

        8. No Rights as a Shareholder. This Warrant does not entitle the Holder
to any voting rights or other rights as a shareholder of the Company prior to
exercise of this Warrant and the payment for the Shares so purchased.
Notwithstanding the foregoing, the Company agrees to transmit to the Holder such
information, documents and reports as are generally distributed to holders of
the capital stock of the Company concurrently with the distribution thereof to
the shareholders. Upon valid exercise of this Warrant and payment for the Shares
so purchased in accordance with the terms of the Warrant, the Holder shall be
deemed a shareholder of the Company.

        9. Sale or Transfer of the Warrant; Legend. The Warrant and the Shares
shall not be sold or transferred unless either (i) they first shall have been
registered under the Act, or (ii) the Company first shall have been furnished
with an opinion of legal counsel reasonably satisfactory to the Company to the
effect that such sale or transfer is exempt from the registration requirements
of the Act. Each certificate representing any Warrant shall bear the legend set
out on page 1 hereof. Each certificate representing any Shares shall bear a
legend substantially in the following form, as appropriate:

                THE SHARES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED
                FOR INVESTMENT AND NOT WITH A VIEW TO, OR IN CONNECTION WITH,
                THE SALE OR DISTRIBUTION THEREOF. NO SUCH SALE OR DISPOSITION
                MAY BE EFFECTED WITHOUT AN EFFECTIVE REGISTRATION STATEMENT
                RELATED THERETO OR AN OPINION OF COUNSEL REASONABLY SATISFACTORY
                TO THE COMPANY THAT SUCH REGISTRATION IS NOT REQUIRED UNDER THE
                SECURITIES ACT OF 1933, AS AMENDED.


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Such Warrant and Shares may be subject to additional restrictions on transfer
imposed under applicable state and federal securities law.

        10. Put Right. Commencing on the date six months from the Original Issue
Date, and prior to the Expiration Date, the Holder shall have the right,
exercised by the delivery of written notice to the Company (a "Put Notice"), to
require the Company to cancel the unexercised portion of this Warrant, and all
related rights in exchange for a cash payment (the "Put Payment") equal to
$0.3525 per share payable to the Holder within ten (10) days of receipt by the
Company of the Put Notice and the original Warrant for cancellation.

        11. Call Option. At any time during the one year period following the
indefeasible payment in full in cash or cash equivalents of the Credit
Obligations, and prior to June 30, 2004, the Company shall have the right
exercised by the delivery of written notice to the Holder (a "Call Notice") to
cancel this Warrant and the purchase rights hereunder in exchange for a cash
payment (the "Call Payment") equal to $0.5288 per share, payable to the Holder
within five (5) days after delivery by the Company of the Call Notice, provided
however, that any payment made pursuant to this Section 11 may only be made out
of a New Financing Source. Notwithstanding anything to the contrary contained
herein, the Holder shall be entitled to exercise this Warrant in whole or in
part at any time after the receipt of the Call Notice until the receipt by the
Holder of the Call Payment. In the event that the Holder chooses to exercise all
or a portion of the Warrant after receipt of the Call Notice, the Company shall
have the option to rescind such Call Notice or to exercise its call option with
respect to that portion of the Warrant which remains unexercised through the
delivery of a pro rata portion of the Call Payment. The Company shall have the
right to exercise the call option set forth herein one time only.

        12. Modifications and Waivers. This Warrant may not be changed, waived,
discharged or terminated except by an instrument in writing signed by the party
against which enforcement of the same is sought.

        13. Notices. Any notice, request or other document required or permitted
to be given or delivered to the Holder or the Company shall be sufficiently
given or made if sent by registered or certified mail, postage prepaid,
addressed to the parties as provided below:


               If to Holder:   Fleet National Bank
                               100 Federal Street, 6th Floor
                               MA DE 10006A
                               Boston, MA  02110
                                Attn:  Michael F. O'Neill
                               Senior Vice President

               with a copy to:

                               Brown, Rudnick, Freed & Gesmer
                               One Financial Center
                               Boston, MA  02111
                               Attn:  William R. Baldiga, Esquire
                                      Mary D. Bucci, Esquire

               If to Company:  Nextera Enterprises, Inc.
                               343 Congress Street
                               Suite 2100
                               Boston, MA  02210-1215
                               Attn: Michael P. Muldowney,
                                     Chief Financial Officer

               with a copy to: Maron & Sandler
                               844 Moraga Drive
                               Los Angeles, CA  90049
                               Attn:  Stanley E. Maron, Esquire


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        14. Loss, Theft, Destruction or Mutilation of Warrant. The Company
covenants with the Holder that upon its receipt of evidence reasonably
satisfactory to the Company of the loss, theft, destruction or mutilation of
this Warrant or any stock certificate and, in the case of any such loss, theft
or destruction, of an indemnity or security reasonably satisfactory to it, and
upon reimbursement to the Company of all reasonable expenses incidental thereto,
and upon surrender and cancellation of this Warrant or stock certificate, if
mutilated, the Company will make and deliver a new Warrant or stock certificate,
of like tenor, in lieu of the lost, stolen, destroyed or mutilated Warrant or
stock certificate.

        15. Representations and Warranties of Holder. By accepting this Warrant,
the Holder represents and warrants that it is acquiring this Warrant and the
Shares for its own account, for investment and not with a view to, or for sale
in connection with, any distribution thereof or any part thereof. Holder
represents and warrants that it is (a) experienced in the evaluation of
businesses similar to the Company, (b) is able to fend for itself in the
transactions contemplated by this Warrant, (c) has such knowledge and experience
in financial and business matters as to be capable of evaluating the merits and
risks of an investment in the Company, (d) has the ability to bear the economic
risks of an investment in the Company, (e) has been furnished with or has had
access to such information as is specified in subparagraph (b)(2) of Rule 502
promulgated under the Act and (f) has been afforded the opportunity to ask
questions of and to receive answers from the Company and to obtain any
additional information necessary to make an informed investment decision with
respect to an investment in the Company. The Holder further represents that it
is an "accredited investor" as defined in Rule 501(a) of Regulation D under the
Act.

        16. Representations and Warranties of Company. The Company represents
that:

               (a) The execution and delivery of this Warrant has been duly
        authorized by the Company's Board of Directors and constitutes the
        legal, valid and binding obligation of the Company enforceable against
        the Company in accordance with its terms, except as enforcement thereof
        may be limited by bankruptcy, insolvency, or other laws affecting the
        enforcement of creditors' rights in general and except that the
        enforceability of the obligations hereunder is subject to general
        principals of equity (regardless of whether such enforceability is
        considered in a proceeding at equity or at law). Neither the execution
        nor the delivery of this Warrant, nor fulfillment of nor compliance with
        the terms and provisions of this Warrant, nor the issuance of Shares
        upon exercise of the Warrant, will violate the terms of the certificate
        of incorporation or by-laws of the Company or, to the best of the
        Company's knowledge, any agreement (including any agreement with
        stockholders), instrument, judgment, decree or statute to which the
        Company is subject.

               (b) As of March 29, 2002, the authorized capital stock of the
        Company consisted of (i) 99,300,000 shares of Common Stock, $0.001 par
        value per share, 95,000,000 shares of which are designated as Class A
        Common Stock, of which 31,885,896 shares are issued and outstanding, and
        4,300,000 shares of which are designated as Class B Common Stock, of
        which 3,869,570 shares are issued and outstanding, and (ii) 10,000,000
        shares of Preferred Stock, $0.001 par value per share 600,000 shares of
        which are designated as Series A Cumulative Convertible Preferred Stock,
        of which 210,000 shares are issued and outstanding.

               (c) Except as set forth in subparagraph (b) above, and in
        registration statements filed by the Company under the Act or in any
        report filed by the Company under the Securities Exchange Act of 1934,
        as amended, the Company has not authorized any rights (either preemptive
        or other) or options to subscribe for or purchase from the Company, or
        any warrants or other agreements providing for or requiring the issuance
        by the Company of, any capital stock or any securities convertible into
        or exchangeable for its capital stock.

               (d) Sufficient shares of authorized but unissued shares of Common
        Stock of the Company have been reserved by appropriate corporate action
        with the prospective exercise of the Warrant, and, the issuance of
        either the Warrant or the shares of Common Stock upon exercise of the
        Warrant will not require any further corporate action by the
        stockholders or directors of the Company, will not be subject to
        preemptive rights (unless the exercise of the same has been irrevocably
        waived) in any present stockholders of the Company and will not conflict
        with any provision of any agreement to


                                       8


<PAGE>
        which the Company is a party or by which it is bound, and such Common
        Stock, when issued upon exercise of the Warrant in accordance with its
        terms, will be duly authorized, fully paid and non-assessable.

        17. Registration Rights.

               (a) Piggy Back Registration Rights. If (but without any
        obligation to do so) the Company shall determine to register (a "Company
        Registration") any of its securities for its own account or for any
        other person (other than a registration under the Act of shares issued
        in connection with any acquisition of any entity or business, shares
        issuable solely upon the exercise of stock options, or shares issuable
        solely pursuant to employee benefit plans or arrangements, including
        registration statements on Form S-4, S-8 or any successor form), the
        Company shall do the following:

                       (i) promptly give the Holder written notice thereof
               (which shall include a list of the jurisdictions in which the
               Company intends to attempt to register or qualify such securities
               under the applicable blue sky or other state securities laws);
               and

                       (ii) include among the securities which it then registers
               or qualifies all Registrable Securities (as defined below)
               specified in a written request or requests, made within fifteen
               (15) days after receipt of the written notice from the Company,
               by the Holder. The Holder shall have the right to withdraw its
               request for inclusion of its Registrable Securities in any
               registration statement by giving written notice to the Company of
               its request to withdraw. The Company may withdraw a Company
               Registration at any time prior to the time it becomes effective
               whether or not the Holder has elected to include Registrable
               Securities (as defined below) in such registration. For purposes
               of this Warrant, the term "Registrable Securities" shall mean all
               shares of Common Stock issued and issuable upon exercise of the
               Warrant; provided however, that shares of Common Stock which are
               "Registrable Securities" shall cease to be Registrable Securities
               (a) upon any sale pursuant to a registration statement under the
               Act, Section 4(1) of the Act or Rule 144 promulgated under the
               Act or (b) at such time as such shares of Common Stock are freely
               saleable under Rule 144(k) promulgated under the Act (or a
               successor provision).

               (b) Limitations of Registration. If and to the extent that the
        Holder shall have, at the time of the delivery of the written request
        referred to in subparagraph (a) above, no present intention of selling
        or distribution, the Company shall be obligated to effect such
        registration, qualification or compliance with respect to the Holder's
        Registrable Securities only if and to the extent, in each case, that
        such registration, qualification and compliance are at the time
        permitted by the applicable statutes or rules and regulations thereunder
        or the practices of the governmental authority concerned.

               (c) Registration Procedures. In the case of each registration,
        qualification or compliance pursuant to this Section 17, the Company
        will keep the Holder advised in writing as to the initiation of
        proceedings for such registration, qualification and compliance and as
        to the completion thereof, and will advise the Holder, upon written
        request, of the progress of such proceedings. At the expense of the
        Company, the Company will (i) keep such registration, qualification and
        compliance current and effective for a period of the earlier of (A) 120
        days, or (B) until the Holder has completed the distributions relating
        thereto, including, without limitation, the filing of post-effective
        amendments and supplements to any registration statement or prospectus,
        as necessary to permit the sale or distribution of Registrable
        Securities not theretofore sold or distributed, and (ii) take all
        necessary action under any applicable blue sky or other state securities
        laws to permit such exercise, sale or distribution, all as reasonably
        requested by such Holder; provided, however, that the Company shall not
        be required in connection therewith to qualify as a foreign corporation
        in any jurisdiction in which it is not now so qualified or to take any
        action that would subject it to general consent to service of


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<PAGE>
        process or taxation. The Company shall not be required to file, cause to
        become effective or maintain the effectiveness of any registration
        statement that contemplates a distribution of securities on a delayed or
        continuous basis pursuant to Rule 415 under the Act.

               (d) Registration Rights. Anything to the contrary in Section 17
        notwithstanding, in connection with any Company Registration, the
        Company shall not be required to include any of the Holder's Registrable
        Securities in such Company Registration unless the Holder accepts the
        terms of the underwriting as agreed upon between the Company and the
        underwriters selected by it (or by other persons entitled to select the
        underwriters), and then only in such quantity as the underwriters
        determine in their sole discretion will not jeopardize the success of
        the offering by the Company or will not adversely affect the aggregate
        proceeds to the Company from the offering. If the total amount of
        securities, including Registrable Securities and all other securities
        requested to be included in such offering by any stockholder of the
        Company, exceeds the amount of securities that the underwriters
        determine in their sole discretion is compatible with the success of the
        offering or the aggregate proceeds to the Company from the offering,
        then the number of Shares to be offered for the account of the Holder
        and all such other persons participating in such registration shall be
        reduced (to zero if necessary) or limited pro rata in proportion to the
        respective number of Shares requested to be registered by the Holder and
        each other person to reduce the total number of Shares requested to be
        included in such offering to the number of Shares, if any, recommended
        by such underwriters.

               (e) Indemnification. The Company will indemnify, defend and hold
        harmless the Holder to the fullest extent that such agreement is
        enforceable under applicable law against all claims, losses, damages and
        liabilities (or actions in respect thereof) arising out of or based on
        any untrue statement (or alleged untrue statement) of material fact
        contained therein (or in any related registration statement,
        notification or the like) or any omission (or alleged omission) to state
        therein a material fact required to be stated therein or necessary to
        make the statements therein not misleading, or any violation by the
        Company of any rule or regulation promulgated under the Act applicable
        to the Company and relating to action or inaction required of the
        Company in connection with any such registration, qualification or
        compliance, and will reimburse the Holder for any legal or any other
        expenses reasonably incurred in connection with investigating or
        defending any such claim, loss, damage, liability or action provided,
        however, that the Company will not be liable in any such case to the
        extent that any such claim, loss, damage or liability arises out of or
        is based on any untrue statement or omission based upon written
        information furnished to the Company by an instrument duly executed by
        the Holder and stated to be specifically for use therein.

               (f) The Holder will indemnify, defend and hold harmless the
        Company to the fullest extent that such agreement is enforceable under
        applicable law against all claims, losses, damages and liabilities (or
        actions in respect thereof) arising out of or based on any untrue
        statement (or alleged untrue statement) of material fact contained
        therein (or in any related registration statement, notification or the
        like) or any omission (or alleged omission) to state therein a material
        fact required to be stated therein or necessary to make the statements
        therein not misleading, or any violation by the Holder of any rule or
        regulation promulgated under the Act applicable to the Holder and
        relating to action or inaction required of the Holder in connection with
        any such registration, qualification or compliance, and will reimburse
        the Company for any legal or any other expenses reasonably incurred in
        connection with investigating or defending any such claim, loss, damage,
        liability or action, in each case to the extent (and only to the extent)
        that such claims, losses, damages, liabilities and actions relate to
        reliance on any untrue statement or omission based upon written
        information furnished to the Company by an instrument duly executed by
        the Holder and stated to be specifically for use in the registration
        statement, provided, however, that such Holder's obligations hereunder
        shall be limited to an amount equal to the proceeds received by such
        Holder of the Registrable Securities sold in such registration.


                                       10


<PAGE>
               (g) Notwithstanding the foregoing, to the extent that the
        provisions on indemnification contained in the underwriting agreement
        entered into in connection with a Company Registration are in conflict
        with the provisions of this Section 17, the provisions in the
        underwriting agreement shall control.

        18. Binding Effect on Successors. This Warrant shall be binding upon any
corporation succeeding the Company by merger, consolidation or acquisition of
all or substantially all of the Company's assets, and all of the obligations of
the Company relating to the Shares issuable upon exercise of this Warrant shall
survive the exercise and termination of this Warrant and all of the covenants
and agreements of the Company shall inure to the benefit of the successors and
assigns of the Holder.

        19. Amendments. No approval, consent, amendment or waiver of this
Agreement shall be effective unless in writing and signed by the Company and
Holder.

        20. Counterparts. This Agreement may be executed in any number of
counterparts and each such counterpart shall for all purposes be deemed to be an
original, and all such counterparts shall together constitute but one and the
same instrument.

        21. Governing Law. This Warrant shall be construed and enforced in
accordance with, and the rights of the parties shall be governed by, the laws of
the Commonwealth of Massachusetts.

        22. Entire Agreement. This Warrant constitutes the entire agreement
among the parties hereto pertaining to the subject matter hereof, and any and
all other written or oral agreements relating to the subject matter hereof
existing among any of the parties hereto are expressly cancelled.


                                       11


<PAGE>
        IN WITNESS WHEREOF, the parties have caused this Warrant to be executed
by their duly authorized representatives as of the date first above written.

                                          NEXTERA ENTERPRISES, INC.,
                                          as Company

                                          By:  /s/ Michael P. Muldowney
                                             --------------------------------
                                             Michael P. Muldowney
                                             Chief Financial Officer

                                          FLEET NATIONAL BANK,
                                          as Agent, Lender and Holder

                                          By:  /s/ M. F. O'Neill
                                             --------------------------------
                                             Michael F. O'Neill
                                             Senior Vice President


                                       12


<PAGE>
                                    EXHIBIT A

                               NOTICE OF EXERCISE

To:     NEXTERA ENTERPRISES, INC.

        1. The undersigned hereby elects to purchase _______ shares of Common
Stock of Nextera Enterprises, Inc. pursuant to the terms of the attached
Warrant, and tenders herewith payment of the purchase price of such shares in
full.

        2. Please issue a certificate or certificates representing said shares
in the name of the undersigned or in such other name or names as are specified
below.

        3. The undersigned represents that the aforesaid shares of Common Stock
are being acquired for the account of the undersigned for investment and not
with a view to, or for resale in connection with, the distribution thereof and
that the undersigned has no present intention of distributing or reselling such
shares. The undersigned further represents that such shares shall not be sold or
transferred unless either (1) they first shall have been registered under the
Securities Act of 1933, as amended, or (ii) the Company first shall have been
furnished with an opinion of legal counsel reasonably satisfactory to the
Company to the effect that such sale or transfer is exempt from the registration
requirement.

        4. In the event of partial exercise, please re-issue an appropriate
Warrant exercisable into the remaining shares.



                                            -------------------------------
                                            (Name)

                                            -------------------------------
                                            (Address)

                                            -------------------------------
                                            (Signature)

                                            -------------------------------
                                            (Date)


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