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                                                                  Exhibit 10.55



                               EXCELON CORPORATION

                            INVESTOR RIGHTS AGREEMENT
                            -------------------------


     This Agreement dated as of June 12, 2001 is entered into by and among
eXcelon Corporation, a Delaware corporation (the "Company"), and the entities
listed on EXHIBIT A attached hereto (the "Purchasers").

                                    ---------
                                    Recitals
                                    --------

     WHEREAS, C-bridge Internet Solutions, Inc., a Delaware corporation
("C-BRIDGE") and the Purchasers entered into a Series A Convertible Preferred
Stock Purchase Agreement dated as of October 7, 1999 (the "Purchase Agreement");

     WHEREAS, in connection with the Purchase Agreement, the Purchasers and
C-bridge entered into a certain Investor Rights Agreement dated as of October 7,
1999 (the "C-bridge Investor Rights Agreement");

     WHEREAS, pursuant to the terms of the C-bridge Investor Rights Agreement,
the Purchasers have certain rights with respect to the registration of shares of
capital stock of C-bridge under the Securities Act (as defined below);

     WHEREAS, pursuant to the terms of that certain Agreement and Plan of
Reorganization among C-Bridge, the Company, and the other parties thereto dated
as of May 22, 2001 (the "Merger Agreement"), the outstanding shares of common
stock of C-bridge shall be converted into shares of Common Stock of the Company;
and

     WHEREAS, the Company desires to grant the Purchasers, among other things,
substantially similar rights with respect to the registration of shares of
Common Stock of the Company under the Securities Act (as defined below), as such
Purchasers currently hold with respect to shares of capital stock of C-bridge.

     NOW, THEREFORE, in consideration of the mutual promises and covenants
contained in this Agreement, the parties hereto agree as follows:

     1. Certain Definitions.

     As used in this Agreement, the following terms shall have the following
respective meanings:

     "Board of Directors" means the Board of Directors of the Company.


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     "C-bridge" shall have the meaning set forth in the recitals.

     "C-bridge Investor Rights Agreement" shall have the meaning set forth in
the recitals.

     "Commission" means the Securities and Exchange Commission, or any other
federal agency at the time administering the Securities Act (as defined below).

     "Common Stock" means the common stock, $0.001 par value per share, of the
Company.

     "Effective Time" shall have the meaning set forth in the Merger Agreement.

     "Exchange Act" means the Securities Exchange Act of 1934, as amended, or
any successor federal statute, and the rules and regulations of the Commission
issued under such Act, as they each may, from time to time, be in effect.

     "Initiating Holders" means the Stockholders initiating a request for
registration pursuant to Section 2.1(a) or 2.1(b), as the case may be.

     "Merger" shall mean the consummation of the transactions set forth in the
Merger Agreement.

     "Merger Agreement" shall have the meaning set forth in the recitals.

     "Other Holders" shall have the meaning set forth in Section 2.1(d).

     "Prospectus" means the prospectus included in any Registration Statement,
as amended or supplemented by an amendment or prospectus supplement, including
post-effective amendments, and all material incorporated by reference or deemed
to be incorporated by reference in such Prospectus.

     "Registration Statement" means a registration statement filed by the
Company with the Commission for a public offering and sale of securities of the
Company (other than a registration statement on Form S-8 or Form S-4, or their
successors, or any other form for a similar limited purpose, or any registration
statement covering only securities proposed to be issued in exchange for
securities or assets of another corporation).

     "Registration Expenses" means the expenses described in Section 2.4.

     "Registrable Shares" means (i) the shares of Common Stock issued or
issuable upon consummation of the Merger and (ii) any other shares of Common
Stock issued in respect of such shares (because of stock splits, stock
dividends, reclassifications, recapitalizations, or similar events); PROVIDED,
HOWEVER, that shares of Common Stock which are Registrable Shares shall cease to
be Registrable Shares upon (i) any sale pursuant to a Registration Statement or
Rule 144 under the Securities Act (as defined below) or (ii) any sale in any
manner to a person or entity which, by virtue of Section 5 of this Agreement, is
not entitled to the rights provided by this Agreement. Wherever reference is
made in this Agreement to a request or consent of


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holders of a certain percentage of Registrable Shares, the determination of such
percentage shall include shares of Common Stock issuable upon conversion of the
Registrable Shares even if such conversion has not been effected.

     "Securities Act" means the Securities Act of 1933, as amended, or any
successor federal statute, and the rules and regulations of the Commission
issued under such Act, as they each may, from time to time, be in effect.

     "Selling Stockholder" means any Stockholder owning Registrable Shares
included in a Registration Statement.

     "Stockholders" means the Purchasers and any persons or entities to whom the
rights granted under this Agreement are transferred by any Purchasers, their
successors or assigns pursuant to Section 5 hereof.

     2. Registration Rights

        2.1 Required Registrations.

     (a) At any time after the Effective Time, the Purchasers may request once
only, in writing, that the Company effect the registration on Form S-1 (or such
successor form), of Registrable Shares having an aggregate value of at least
$1,000,000 (based on the then current public market price); PROVIDED, HOWEVER,
that if the Company is eligible to file a Registration Statement on Form S-3 (or
any successor form relating to secondary offerings), such registration may be
effected on Form S-3 (or any successor form relating to secondary offerings).

     (b) At any time after the Company becomes eligible to file a Registration
Statement on Form S-3 (or any successor form relating to secondary offerings), a
Stockholder or Stockholders holding in the aggregate at least 25% of the
Registrable Shares then outstanding may request, in writing, that the Company
effect the registration (which may, at such Stockholder's request, be a shelf
registration pursuant to Rule 415 of the Securities Act) on Form S-3 (or such
successor form), of Registrable Shares having an aggregate value of at least
$1,000,000 (based on the then current public market price).

     (c) Upon receipt of any request for registration pursuant to this Section
2, the Company shall promptly give written notice of such proposed registration
to all other Stockholders. Such Stockholders shall have the right, by giving
written notice to the Company within 30 days after the Company provides its
notice, to elect to have included in such registration such of their Registrable
Shares as such Stockholders may request in such notice of election, subject in
the case of an underwritten offering to the approval of the managing underwriter
as provided in Section 2.1(d) below. Thereupon, the Company shall, as
expeditiously as possible, use its best efforts to effect the registration on an
appropriate registration form of all Registrable Shares which the Company has
been requested to so register (provided, however, that in the case of a
registration requested under Sections 2.1(a) or (b), the Company will only be
obligated to effect such registration on Form S-3 (or any successor form).

     (d) If the Initiating Holders intend to distribute the Registrable Shares
covered by their request by means of an underwriting, they shall so advise the
Company as a part of their


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request made pursuant to Sections 2.1(a) or (b), and the Company shall include
such information in its written notice referred to in Section 2.1(c). The right
of any other Stockholder to include its Registrable Shares in such registration
pursuant to Sections 2.1(a) or (b) shall be conditioned upon such other
Stockholder's participation in such underwriting on the terms set forth herein.

     If the Company desires that any officers or directors of the Company
holding securities of the Company be included in any registration for an
underwritten offering requested pursuant to Section 2.1(d) or if other holders
of securities of the Company who are entitled, by contract with the Company, to
have securities included in such a registration (the "Other Holders") request
such inclusion, the Company may include the securities of such officers,
directors and Other Holders in such registration and underwriting on the terms
set forth herein. The Company shall (together with all Stockholders, officers,
directors and Other Holders proposing to distribute their securities through
such underwriting) enter into an underwriting agreement in customary form
(including, without limitation, customary indemnification and contribution
provisions on the part of the Company) with the managing underwriter; provided,
however, that such underwriting agreement shall not provide for indemnification
or contribution obligations on the part of Stockholders materially greater than
the obligations of the Stockholders pursuant to Section 2.5. Notwithstanding any
other provision of this Section 2.1(d), if the managing underwriter advises the
Company that the inclusion of all shares requested to be registered would
adversely affect the offering, the securities of the Company held by any
stockholder other than the Purchasers shall be excluded from such registration
and underwriting to the extent deemed advisable by the managing underwriter, and
if a further limitation of the number of shares is required, the number of
shares that may be included in such registration and underwriting shall be
allocated among all holders of Registrable Shares requesting registration in
proportion, as nearly as practicable, to the respective number of Registrable
Shares held by them at the time of the request for registration made by the
Initiating Holders pursuant to Sections 2.1(a) or (b). If any holder of
Registrable Shares, officer, director or Other Holder who has requested
inclusion in such registration as provided above disapproves of the terms of the
underwriting, such person may elect to withdraw therefrom by written notice to
the Company, and the securities so withdrawn shall also be withdrawn from
registration. If the managing underwriter has not limited the number of
Registrable Shares or other securities to be underwritten, the Company may
include securities for its own account in such registration if the managing
underwriter so agrees and if the number of Registrable Shares and other
securities which would otherwise have been included in such registration and
underwriting will not thereby be limited.

     (e) The Company shall have the right to select the managing underwriter(s)
for any underwritten offering requested pursuant to Sections 2.1(a) or (b),
subject to the approval of the Initiating Holders, which approval will not be
unreasonably withheld or delayed.

     (f) The Company shall not be required to effect more than three (3)
registrations pursuant to Section 2.1(a) or (b). In addition, the Company shall
not be required to effect any registration (other than on Form S-3 or any
successor form relating to secondary offerings) within six months after the
effective date of any other Registration Statement of the Company. For purposes
of this Section 2.1(f), a Registration Statement shall not be counted until such
time as such Registration Statement has been declared effective by the
Commission (unless the Initiating Holders withdraw their request for such
registration (other than as a result of


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information concerning the business or financial condition of the Company which
is made known to the Stockholders after the date on which such registration was
requested) and elect not to pay the Registration Expenses therefor pursuant to
Section 2.4).

     (g) If at the time of any request to register Registrable Shares by
Initiating Holders pursuant to this Section 2.1, the Company is engaged or has
plans to engage in a registered public offering or is engaged in any other
activity which, in the good faith determination of the Company's Board of
Directors, would be adversely affected by the requested registration, then the
Company may at its option direct that such request be delayed for a period not
in excess of 90 days from the date of such request, such right to delay a
request to be exercised by the Company not more than once in any 12-month
period.

         2.2 Incidental Registration.

     (a) Whenever the Company proposes to file a Registration Statement (other
than a Registration Statement filed pursuant to Section 2.1, a Registration
Statement covering shares to be sold solely for the account of Other Holders, or
a Registration Statement on Form S-4, Form S-8 or any successor form thereto) at
any time and from time to time, it will, prior to such filing, give written
notice to all Stockholders of its intention to do so. Upon the written request
of a Stockholder or Stockholders given within 20 days after the Company provides
such notice (which request shall state the intended method of disposition of
such Registrable Shares), the Company shall use its best efforts to cause all
Registrable Shares which the Company has been requested by such Stockholder or
Stockholders to register to be registered under the Securities Act to the extent
necessary to permit their sale or other disposition in accordance with the
intended methods of distribution specified in the request of such Stockholder or
Stockholders; provided that the Company shall have the right to postpone or
withdraw any registration effected pursuant to this Section 2.2 without
obligation to any Stockholder.

     (b) If the registration for which the Company gives notice pursuant to
Section 2.2(a) is a registered public offering involving an underwriting, the
Company shall so advise the Stockholders as a part of the written notice given
pursuant to Section 2.2(a) or (b). In such event, the right of any Stockholder
to include its Registrable Shares in such registration pursuant to Section 2.2
shall be conditioned upon such Stockholder's participation in such underwriting
on the terms set forth herein. All Stockholders proposing to distribute their
securities through such underwriting shall enter into an underwriting agreement
in customary form with the underwriter or underwriters selected for the
underwriting by the Company. Notwithstanding any other provision of this Section
2.2, if the managing underwriter determines that the inclusion of all shares
requested to be registered would adversely affect the offering, the Company may
limit the number of Registrable Shares to be included in the registration and
underwriting. The Company shall so advise all holders of Registrable Shares
requesting registration, and the number of shares that are entitled to be
included in the registration and underwriting shall be allocated in the
following manner. The securities of the Company held by holders other than
Stockholders and Other Holders shall be excluded from such registration and
underwriting to the extent deemed advisable by the managing underwriter, and, if
a further limitation on the number of shares is required, the number of shares
that may be included in such registration and underwriting shall be allocated
among all Stockholders and Other Holders requesting registration in proportion,
as nearly as practicable, to the respective number of shares of Common Stock (on
an as-converted


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basis) which they held at the time the Company gives the notice specified in
Section 2.2(a). If any Stockholder or Other Holder would thus be entitled to
include more securities than such holder requested to be registered, the excess
shall be allocated among other requesting Stockholders and Other Holders pro
rata in the manner described in the preceding sentence. If any holder of
Registrable Shares or any officer, director or Other Holder disapproves of the
terms of any such underwriting, such person may elect to withdraw therefrom by
written notice to the Company, and any Registrable Shares or other securities
excluded or withdrawn from such underwriting shall be withdrawn from such
registration.

     (c) Notwithstanding the foregoing, the Company shall not be required,
pursuant to this Section 2.2, to include any Registrable Shares in a
Registration Statement if such Registrable Shares can then be sold pursuant to
Rule 144(k) under the Securities Act.

         2.3 Registration Procedures.

     (a) If and whenever the Company is required by the provisions of this
Agreement to use its best efforts to effect the registration of any Registrable
Shares under the Securities Act, the Company shall:

          (i) file with the Commission a Registration Statement with respect to
     such Registrable Shares and use its best efforts to cause that Registration
     Statement to become effective as soon as possible;

          (ii) as expeditiously as possible prepare and file with the Commission
     any amendments and supplements to the Registration Statement and the
     prospectus included in the Registration Statement as may be necessary to
     comply with the provisions of the Securities Act (including the anti-fraud
     provisions thereof) and to keep the Registration Statement effective for 24
     months from the effective date or such lesser period until all such
     Registrable Shares are sold;

          (iii) as expeditiously as possible furnish to each Selling Stockholder
     such reasonable numbers of copies of the Prospectus, including any
     preliminary Prospectus, in conformity with the requirements of the
     Securities Act, and such other documents as such Selling Stockholder may
     reasonably request in order to facilitate the public sale or other
     disposition of the Registrable Shares owned by such Selling Stockholder;

          (iv) as expeditiously as possible use its best efforts to register or
     qualify the Registrable Shares covered by the Registration Statement under
     the securities or Blue Sky laws of such states as the Selling Stockholders
     shall reasonably request, and do any and all other acts and things that may
     be necessary or desirable to enable the Selling Stockholders to consummate
     the public sale or other disposition in such states of the Registrable
     Shares owned by the Selling Stockholder; provided, however, that the
     Company shall not be required in connection with this paragraph (iv) to
     qualify as a foreign corporation or execute a general consent to service of
     process in any jurisdiction;

          (v) as expeditiously as possible, cause all such Registrable Shares to
     be listed on each securities exchange or automated quotation system on
     which similar securities issued by the Company are then listed;


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          (vi) promptly provide a transfer agent and registrar for all such
     Registrable Shares not later than the effective date of such registration
     statement;

          (vii) promptly make available for inspection by the Selling
     Stockholders, any managing underwriter participating in any disposition
     pursuant to such Registration Statement, and any attorney or accountant or
     other agent retained by any such underwriter or selected by the Selling
     Stockholders, all financial and other records, pertinent corporate
     documents and properties of the Company and cause the Company's officers,
     directors, employees and independent accountants to supply all information
     reasonably requested by any such seller, underwriter, attorney, accountant
     or agent in connection with such Registration Statement;

          (viii) as expeditiously as possible, notify each Selling Stockholder,
     promptly after it shall receive notice thereof, of the time when such
     Registration Statement has become effective or a supplement to any
     Prospectus forming a part of such Registration Statement has been filed;
     and

          (ix) as expeditiously as possible following the effectiveness of such
     Registration Statement, notify each seller of such Registrable Shares of
     any request by the Commission for the amending or supplementing of such
     Registration Statement or Prospectus.

     (b) If the Company has delivered a Prospectus to the Selling Stockholders
and after having done so the Prospectus is amended to comply with the
requirements of the Securities Act, the Company shall promptly notify the
Selling Stockholders and, if requested, the Selling Stockholders shall
immediately cease making offers of Registrable Shares and return all
Prospectuses to the Company. The Company shall promptly provide the Selling
Stockholders with revised Prospectuses and, following receipt of the revised
Prospectuses, the Selling Stockholders shall be free to resume making offers of
the Registrable Shares.

     (c) In the event that, in the reasonable judgment of the Company, it is
advisable to suspend use of a Prospectus included in a Registration Statement
due to pending material developments or other events that have not yet been
publicly disclosed and as to which the Company believes public disclosure would
be detrimental to the Company, the Company shall notify all Selling Stockholders
to such effect, and, upon receipt of such notice, each such Selling Stockholder
shall immediately discontinue any sales of Registrable Shares pursuant to such
Registration Statement until such Selling Stockholder has received copies of a
supplemented or amended Prospectus or until such Selling Stockholder is advised
in writing by the Company that the then current Prospectus may be used and has
received copies of any additional or supplemental filings that are incorporated
or deemed incorporated by reference in such Prospectus. Notwithstanding anything
to the contrary herein, the Company shall not exercise its rights under this
Section 2.3(c) to suspend sales of Registrable Shares for a period in excess of
90 days in any 365-day period.


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          2.4 Allocation of Expenses.

     The Company will pay all Registration Expenses for all registrations under
this Agreement; provided, however, that if a registration under Section 2.1 is
withdrawn at the request of the Initiating Holders (other than as a result of
information concerning the business or financial condition of the Company which
is made known to the Stockholders after the date on which such registration was
requested) and if the Initiating Holders elect not to have such registration
counted as a registration requested under Section 2.1, the requesting
Stockholders shall pay the Registration Expenses of such registration pro rata
in accordance with the number of their Registrable Shares included in such
registration. For purposes of this Section, the term

     "Registration Expenses" shall mean all expenses incurred by the Company in
complying with this Agreement, including, without limitation, all registration
and filing fees, exchange listing fees, printing expenses, fees and expenses of
counsel for the Company and the fees and expenses of one counsel selected by the
Selling Stockholders to represent the Selling Stockholders, state Blue Sky fees
and expenses, and the expense of any special audits incident to or required by
any such registration, but excluding underwriting discounts, selling commissions
and the fees and expenses of Selling Stockholders' own counsel (other than the
counsel selected to represent all Selling Stockholders).

          2.5 Indemnification and Contribution.

     (a) In the event of any registration of any of the Registrable Shares under
the Securities Act pursuant to this Agreement, the Company will indemnify and
hold harmless each Selling Stockholder, each underwriter of such Registrable
Shares, and each other person, if any, who controls such Selling Stockholder or
underwriter within the meaning of the Securities Act or the Exchange Act against
any losses, claims, damages or liabilities, joint or several, to which such
Selling Stockholder, underwriter or controlling person may become subject under
the Securities Act, the Exchange Act, state securities or Blue Sky laws or
otherwise, insofar as such losses, claims, damages or liabilities (or actions in
respect thereof) arise out of or are based upon any untrue statement or alleged
untrue statement of any material fact contained in any Registration Statement
under which such Registrable Shares were registered under the Securities Act,
any preliminary prospectus or final prospectus contained in the Registration
Statement, or any amendment or supplement to such Registration Statement, or
arise out of or are based upon the omission or alleged omission to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading; and the Company will reimburse such Selling Stockholder,
underwriter and each such controlling person for any legal or any other expenses
reasonably incurred by such Selling Stockholder, underwriter or controlling
person in connection with investigating or defending any such loss, claim,
damage, liability or action; provided, however, that the Company will not be
liable in any such case to the extent that any such loss, claim, damage or
liability arises out of or is based upon any untrue statement or omission made
in such Registration Statement, preliminary prospectus or prospectus, or any
such amendment or supplement, in reliance upon and in conformity with
information furnished to the Company, in writing, by or on behalf of such
Selling Stockholder, underwriter or controlling person specifically for use in
the preparation thereof.


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     (b) In the event of any registration of any of the Registrable Shares under
the Securities Act pursuant to this Agreement, each Selling Stockholder,
severally and not jointly, will indemnify and hold harmless the Company, each of
its directors and officers and each underwriter (if any) and each person, if
any, who controls the Company or any such underwriter within the meaning of the
Securities Act or the Exchange Act, against any losses, claims, damages or
liabilities, joint or several, to which the Company, such directors and
officers, underwriter or controlling person may become subject under the
Securities Act, Exchange Act, state securities or Blue Sky laws or otherwise,
insofar as such losses, claims, damages or liabilities (or actions in respect
thereof) arise out of or are based upon any untrue statement or alleged untrue
statement of a material fact contained in any Registration Statement under which
such Registrable Shares were registered under the Securities Act, any
preliminary prospectus or final prospectus contained in the Registration
Statement, or any amendment or supplement to the Registration Statement, or
arise out of or are based upon any omission or alleged omission to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading, if the statement or omission was made in reliance upon
and in conformity with information relating to such Selling Stockholder
furnished in writing to the Company by or on behalf of such Selling Stockholder
specifically for use in connection with the preparation of such Registration
Statement, prospectus, amendment or supplement; provided, however, that the
obligations of a Selling Stockholder hereunder shall be limited to an amount
equal to the net proceeds to such Selling Stockholder of Registrable Shares sold
in connection with such registration.

     (c) Each party entitled to indemnification under this Section (the
"Indemnified Party") shall give notice to the party required to provide
indemnification (the "Indemnifying Party") promptly after such Indemnified Party
has actual knowledge of any claim as to which indemnity may be sought, and shall
permit the Indemnifying Party to assume the defense of any such claim or any
litigation resulting therefrom; provided, however, that counsel for the
Indemnifying Party, who shall conduct the defense of such claim or litigation,
shall be approved by the Indemnified Party (whose approval shall not be
unreasonably withheld); and, provided, further, that the failure of any
Indemnified Party to give notice as provided herein shall not relieve the
Indemnifying Party of its obligations under this Section except to the extent
that the Indemnifying Party is adversely affected by such failure. The
Indemnified Party may participate in such defense at such party's expense;
provided, however, that the Indemnifying Party shall pay such expense if
representation of such Indemnified Party by the counsel retained by the
Indemnifying Party would be inappropriate due to actual or potential differing
interests between the Indemnified Party and any other party represented by such
counsel in such proceeding; provided further that in no event shall the
Indemnifying Party be required to pay the expenses of more than one law firm per
jurisdiction as counsel for the Indemnified Party. The Indemnifying Party also
shall be responsible for the expenses of such defense if the Indemnifying Party
does not elect to assume such defense. No Indemnifying Party, in the defense of
any such claim or litigation shall, except with the consent of each Indemnified
Party, consent to entry of any judgment or enter into any settlement which does
not include as an unconditional term thereof the giving by the claimant or
plaintiff to such Indemnified Party of a release from all liability in respect
of such claim or litigation, and no Indemnified Party shall consent to entry of
any judgment or settle such claim or litigation without the prior written
consent of the Indemnifying Party, which consent shall not be unreasonably
withheld.


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     (d) In order to provide for just and equitable contribution in
circumstances in which the indemnification provided for in this Section 2.5 is
due in accordance with its terms but for any reason is held to be unavailable to
an Indemnified Party in respect to any losses, claims, damages and liabilities
referred to herein, then the Indemnifying Party shall, in lieu of indemnifying
such Indemnified Party, contribute to the amount paid or payable by such
Indemnified Party as a result of such losses, claims, damages or liabilities to
which such party may be subject in such proportion as is appropriate to reflect
the relative fault of the Company on the one hand and the Selling Stockholders
on the other in connection with the statements or omissions which resulted in
such losses, claims, damages or liabilities, as well as any other relevant
equitable considerations. The relative fault of the Company and the Selling
Stockholders shall be determined by reference to, among other things, whether
the untrue or alleged untrue statement of material fact related to information
supplied by the Company or the Selling Stockholders and the parties' relative
intent, knowledge, access to information and opportunity to correct or prevent
such statement or omission. The Company and the Selling Stockholders agree that
it would not be just and equitable if contribution pursuant to this Section 2.5
were determined by pro rata allocation or by any other method of allocation
which does not take account of the equitable considerations referred to above.

     Notwithstanding the provisions of this paragraph of Section 2.5, (a) in no
case shall any one Selling Stockholder be liable or responsible for any amount
in excess of the net proceeds received by such Selling Stockholder from the
offering of Registrable Shares and (b) the Company shall be liable and
responsible for any amount in excess of such proceeds; provided, however, that
no person guilty of fraudulent misrepresentation (within the meaning of Section
11(f) of the Securities Act) shall be entitled to contribution from any person
who was not guilty of such fraudulent misrepresentation. Any party entitled to
contribution will, promptly after receipt of notice of commencement of any
action, suit or proceeding against such party in respect of which a claim for
contribution may be made against another party or parties under this Section,
notify such party or parties from whom contribution may be sought, but the
omission so to notify such party or parties from whom contribution may be sought
shall not relieve such party from any other obligation it or they may have
thereunder or otherwise under this Section. No party shall be liable for
contribution with respect to any action, suit, proceeding or claim settled
without its prior written consent, which consent shall not be unreasonably
withheld.

          2.6 Other Matters with Respect to Underwritten Offerings.

     In the event that Registrable Shares are sold pursuant to a Registration
Statement in an underwritten offering pursuant to Section 2.1, the Company
agrees to (a) enter into an underwriting agreement containing customary
representations and warranties with respect to the business and operations of
the Company and customary covenants and agreements to be performed by the
Company, including without limitation customary provisions with respect to
indemnification by the Company of the underwriters of such offering; (b) use its
best efforts to cause its legal counsel to render customary opinions to the
underwriters with respect to the Registration Statement; and (c) use its best
efforts to cause its independent public accounting firm to issue customary "cold
comfort letters" to the underwriters with respect to the Registration Statement.


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          2.7 Information by Holder.

     Each holder of Registrable Shares included in any registration shall
furnish to the Company such information regarding such holder and the
distribution proposed by such holder as the Company may reasonably request in
writing and as shall be required in connection with any registration,
qualification or compliance referred to in this Agreement.

          2.8 Confidentiality of Notices.

     Any Stockholder receiving any written notice from the Company regarding the
Company's plans to file a Registration Statement shall treat such notice
confidentially and shall not disclose such information to any person other than
as necessary to exercise its rights under this Agreement.

          2.9 Intentionally Omitted.

          2.10 Intentionally Omitted.

          2.11 Rule 144 Requirements. After the earliest of (i) the closing of
the sale of securities of the Company pursuant to a Registration Statement, (ii)
the registration by the Company of a class of securities under Section 12 of the
Exchange Act, or (iii) the issuance by the Company of an offering circular
pursuant to Regulation A under the Securities Act, the Company agrees to:

     (a) make and keep current public information about the Company available,
as those terms are understood and defined in Rule 144;

     (b) use its best efforts to file with the Commission in a timely manner all
reports and other documents required of the Company under the Securities Act and
the Exchange Act (at any time after it has become subject to such reporting
requirements); and

     (c) furnish to any holder of Registrable Shares upon request (i) a written
statement by the Company as to its compliance with the reporting requirements of
Rule 144 and of the Securities Act and the Exchange Act (at any time after it
has become subject to such reporting requirements), (ii) a copy of the most
recent annual or quarterly report of the Company, and (iii) such other reports
and documents of the Company as such holder may reasonably request to avail
itself of any similar rule or regulation of the Commission allowing it to sell
any such securities without registration.


                                       11


<PAGE>


          2.12 Termination. All of the Company's obligations to register
Registrable Shares under Sections 2.1 and 2.2 of this Agreement shall terminate
on December 17, 2004.

     3. Intentionally Omitted.

     4. Intentionally Omitted.

     5. Transfers of Rights.

     This Agreement, and the rights and obligations of each Purchaser hereunder,
may be assigned by such Purchaser to (i) any person or entity to which at least
125,000 Registrable Shares are transferred by such Purchaser or (ii) to any
affiliate, limited partner or general partner of such Purchaser, and such
transferee shall be deemed a "Purchaser" for purposes of this Agreement;
provided that the transferee provides written notice of such assignment to the
Company and agrees in writing to be bound hereby.

     6. General.

     (a) Severability. The invalidity or unenforceability of any provision of
this Agreement shall not affect the validity or enforceability of any other
provision of this Agreement.

     (b) Specific Performance. In addition to any and all other remedies that
may be available at law in the event of any breach of this Agreement, each
Purchaser shall be entitled to specific performance of the agreements and
obligations of the Company hereunder and to such other injunctive or other
equitable relief as may be granted by a court of competent jurisdiction.

     (c) Governing Law. This Agreement shall be governed by and construed in
accordance with the internal laws of the State of Delaware (without reference to
the conflicts of law provisions thereof).

     (d) Notices. All notices, requests, consents, and other communications
under this Agreement shall be in writing and shall be deemed delivered (i) two
business days after being sent by registered or certified mail, return receipt
requested, postage prepaid or (ii) one business day after being sent via a
reputable nationwide overnight courier service guaranteeing next business day
delivery, in each case to the intended recipient as set forth below:

     If to the Company, at eXcelon Corporation, 25 Mall Road, Burlington,
Massachusetts 01803, Attention: Robert N. Goldman, or at such other address or
addresses as may have been furnished in writing by the Company to the
Purchasers, with a copy to Foley, Hoag & Eliot, LLP, One Post Office Square,
Boston, Massachusetts 02109, Attention: John D. Patterson, Jr., Esq.; or

     If to a Purchaser, at his or its address set forth on EXHIBIT A, or at such
other address or addresses as may have been furnished to the Company in writing
by such Purchaser, with a copy to O'Sullivan Graev & Karabell, LLP, 30
Rockefeller Plaza, New York, New York 10112, Attention: Ilan S. Nissan, Esq.


                                       12


<PAGE>


     Any party may give any notice, request, consent or other communication
under this Agreement using any other means (including, without limitation,
personal delivery, messenger service, telecopy, first class mail or electronic
mail), but no such notice, request, consent or other communication shall be
deemed to have been duly given unless and until it is actually received by the
party for whom it is intended. Any party may change the address to which
notices, requests, consents or other communications hereunder are to be
delivered by giving the other parties notice in the manner set forth in this
Section.

     (e) Complete Agreement. This Agreement constitutes the entire agreement and
understanding of the parties hereto with respect to the subject matter hereof
and supersedes all prior agreements and understandings relating to such subject
matter.

     (f) Amendments and Waivers. Any term of this Agreement may be amended or
terminated and the observance of any term of this Agreement may be waived
(either generally or in a particular instance and either retroactively or
prospectively), with the written consent of the Company and the holders of at
least 50% of the Registrable Shares held by all of the Stockholders; PROVIDED,
HOWEVER, that this Agreement may be amended with the consent of the holders of
less than all Registrable Shares only in a manner which applies to all such
holders in the same fashion. Any such amendment, termination or waiver effected
in accordance with this Section 6(f) shall be binding on all parties hereto,
even if they do not execute such consent. No waivers of or exceptions to any
term, condition or provision of this Agreement, in any one or more instances,
shall be deemed to be, or construed as, a further or continuing waiver of any
such term, condition or provision.

     (g) Pronouns. Whenever the context may require, any pronouns used in this
Agreement shall include the corresponding masculine, feminine or neuter forms,
and the singular form of nouns and pronouns shall include the plural, and vice
versa.

     (h) Counterparts; Facsimile Signatures. This Agreement may be executed in
any number of counterparts, each of which shall be deemed to be an original, and
all of which together shall constitute one and the same document. This Agreement
may be executed by facsimile signatures.

     (i) Section Headings. The section headings are for the convenience of the
parties and in no way alter, modify, amend, limit or restrict the contractual
obligations of the parties.


                                       13


<PAGE>


     (j) Effectiveness. The Company shall have no obligations hereunder until
the Effective Time. This Agreement shall automatically terminate and be of no
further force or effect upon a termination of the Merger Agreement pursuant to
Section 7.1 thereof.

     (k) Authority. The Company has all requisite corporate power and authority
to execute, deliver and perform this Agreement and to consummate the
transactions contemplated by this Agreement. The execution, delivery and
performance by the Company of this Agreement has been duly authorized by all
requisite corporate action of the Company, and constitutes a valid and binding
obligation of the Company, enforceable against the Company in accordance with
its terms. The Company's execution, delivery and performance of this Agreement,
its consummation of the transactions contemplated hereby and its compliance with
the provisions hereof will not (i) violate any provision of any law applicable
to the Company or any of its properties or assets or (ii) conflict with or
result in any breach of any of the terms, conditions or provisions of, or
constitute (with due notice or lapse of time, or both) a default or give rise to
any right of termination, cancellation or acceleration under, or result in the
creation of any encumbrance upon any of the properties or assets of the Company
or under the Certificate of Incorporation or By-laws or any oral or written
contract or other agreement or understanding to which the Company is a party
(including, without limitation, any such contract or other agreement enabling
any person or entity to cause or participate in any Registration Statement of
the Company). Except in connection with the Merger or any Registration Statement
filed on Form S-8, the Company is not party to any oral or written contract or
other agreement or understanding pursuant to which the Company has granted or
will grant any person or entity the right to cause of participate in any
Registration Statement of the Company.

     (l) No Conflicts. No consent, approval or authorization of, or declaration
to or filing with, any person or entity is required for the valid authorization,
execution and delivery by the Company of this Agreement or for its consummation
of the transactions contemplated hereby, other than those consents, approvals,
authorizations, declarations or filings which have been obtained or made, as the
case may be.

     Executed as of the date first written above.


                                       COMPANY:

                                       EXCELON CORPORATION

                                       By: /s/ Lacey Brandt
                                       ------------------------------------
                                       Name:  Lacey Brandt
                                       Title: CFO




<PAGE>


                                   PURCHASERS:

                                   INSIGHT CAPITAL PARTNERS III, L.P.

                                   By:  InSight Venture Associates III, L.L.C.,
                                   its General Partner

                                   By: /s/ Scott Maxwell
                                   ----------------------------------
                                   Name:  Scott Maxwell
                                   Title: Managing Member

                                   INSIGHT CAPITAL PARTNERS (CAYMAN) III, L.P.

                                   By:  InSight Venture Associates III, L.L.C.,
                                   its General Partner

                                   By: /s/ Scott Maxwell
                                   ------------------------------------
                                   Name:  Scott Maxwell
                                   Title:

                                   INSIGHT CAPITAL PARTNERS III -
                                   CO-INVESTORS, L.P.

                                   By:  InSight Venture Associates III, L.L.C.,
                                   its General Partner

                                   By: /s/ Scott Maxwell
                                   ------------------------------------
                                   Name:  Scott Maxwell
                                   Title:


<PAGE>


                                    EXHIBIT A

                               LIST OF PURCHASERS

Name and Address
     of Purchaser


InSight Capital Partners III, L.P.
680 Fifth Avenue
9th Floor
New York, New York 10019
Attention: Blair Flicker, Esq.

InSight Capital Partners (Cayman)III, L.P.
c/o W.S. Walker & Company
Walker House
P.O. Box 265GT
Mary Street
George Town
Grand Cayman, Cayman Islands

InSight Capital Partners III -
Co-Investors, L.P.
680 Fifth Avenue
9th Floor
New York, New York 10019
Attention: Blair Flicker, Esq.