<PAGE>   1
                                                                EXHIBIT 10.3

                                PLEDGE AGREEMENT

THIS PLEDGE AGREEMENT ("AGREEMENT") is made as of the 10th day of September,
1996, by and between National Insurance Group, a California Corporation
("Pledgor"), and Imperial Bank ("Secured Party").

                             INTRODUCTORY STATEMENT

A. Secured Party and Pledgor have entered into those certain credit terms and
conditions of even, date herewith (the "Loan Agreement").

B. To induce Secured Party to enter into the Loan Agreement, Pledgor has agreed
to grant to Secured Party, and to create in favor of Secured Party, a security
interest in certain property of Pledgor, as hereinafter provided, as security
for Pledgor's payment and performance of its obligations to Secured Party under
the Loan Agreement.

        Accordingly, the parties hereto hereby agree as follows:

                                    ARTICLE I
                                   COLLATERAL

Section 1.1 Grant of Security Interest in Collateral. In order to secure the due
and punctual payment and performance of Pledgor's obligations under the Loan
Agreement and this Agreement (The "Obligations"), Pledgor hereby pledges to
Secured Party, and grants to Secured Party a security interest in, all of
Pledgor's right, title and interest in, to and under the following property.

        (a) all of Pledgor's right, title and interest in and to 1000 shares of
capital stock of Pinnacle Data Corporation, evidenced by certificate No. 201
(the "Pledged Collateral"), and all distributions or payments of any type,
whether in cash or kind, on account of or otherwise related thereto, and any
securities or other equity interests therein as a result of a merger,
reorganization, or any other activity; and

        (b) All proceeds and products of the foregoing.

The interest in property described in paragraphs (a) and (b) of this Section 1.1
are sometimes referred to herein collectively as the "Collateral."



<PAGE>   2


                                    ARTICLE 2

                                PLEDGOR'S GENERAL
                    REPRESENTATIONS, WARRANTIES AND COVENANTS

        Pledgor represents and warrants, and covenants and agrees that it will
do the following:

        Section 2.1 Title. Pledgor has and will at all times have and maintain
good title to all Collateral free of all security interests, liens and
encumbrances. The liens and security interests granted hereunder will be
perfected on or prior to the date hereof by delivery of the certificates
representing the Pledged Collateral to Secured Party each certificates
evidencing any of the Pledged Collateral pledged hereunder by Pledgor is issued
in the name of Pledgor and has attached an appropriate instrument of transfer
duly signed in blank by Pledgor.

        Section 2.2 Preservation of Rights. Pledgor shall at its expense protect
and defend its rights in the Collateral as described in Section 2.1, and the
security interests of Secured Party therein and thereto, against the claims and
demands of third parties.

        Section 2.3 No Consent. No authorization, approval or other action by,
and no notice to or filing with, any governmental authority or regulatory body
or other person is required for the pledge by Pledgor of the Collateral pursuant
to this Agreement or for the execution, delivery or performance of this
Agreement by Pledgor. The making and performance of this Agreement are within
Pledgor's corporate power and authority and have been duly authorized by all
necessary action of Pledgor.

        Section 2.4 Perfection or Liens. Pledgor has caused and shall cause to
be taken all actions as may be required by any present or future law in order
fully to protect and perfect the liens and security interests of Secured Party
hereof upon, and the rights and interests of Secured Party in, the Collateral.
The security interest created hereby represents a first priority lien on and
security interest in the Collateral.

        Section 2.5 Other Assurances. Pledgor upon request shall take such
actions and deliver such documents as may be reasonably requested by Secured
Party.

        Section 2.6 Release of Collateral. Pledgor shall not sell, transfer,
pledge or otherwise dispose of any of the Collateral or any interest therein, or
attempt or contract to do so.



<PAGE>   3



                                    ARTICLE 3

                   PARTICULAR PROVISIONS RESPECTING COLLATERAL


        (a) Provided no Event of Default shall have occurred and be continuing,
Pledgor shall be entitled, from time to time, to collect, receive and retain for
its own use all distributions and other payments of any type or nature made upon
or with respect to the Collateral (collectively, the "Pledged Collateral
Payments"). Secured Party shall have the right to collect, receive and retain as
Collateral all Pledged Collateral Payments made after the occurrence and during
the continuation of an Event of Default, and Pledgor shall take all such action
as may be reasonably necessary or appropriate to give effect to such right.


        (b) Provided no Event of Default shall have occurred and be continuing,
Pledgor shall have the right, and, after the occurrence and during the
continuation of an Event of Default and following notice from Secured Party to
Pledgor, Secured Party shall have the right, from time to time, to (I) exercise
any and all voting power with respect to the Pledged Collateral, and (ii) give
all consents, ratifications, approvals and waivers with respect to the Pledged
Collateral and to exercise any options or rights with respect thereto.

        Section 3.3 Secured Party's Appointment as Attorney-in Fact.

        (a) Subject to Section 3.3 (b), Pledgor hereby irrevocably constitutes
and appoints Secured Party and any officer of Secured Party and any agent
designated by such officer, with full power of substitution, as its true and
lawful attorney-in-fact with full irrevocable except as set forth in Section 3.3
(b) power and authority in the place and stead of Pledgor and in the name of
Pledgor, or in its own name, from time to time in Secured Party's reasonable
discretion, for the purpose of carrying out the terms of this Agreement, to take
any and all appropriate action and to execute and deliver any and all documents
and instruments which may be reasonably necessary or desirable to accomplish the
purposes of this Agreement.

        (b) Secured Party agrees that, except after the occurrence and during
the continuation of an Event or Default and the acceleration of the Obligations,
it will forebear from exercising the power of attorney or any rights granted to
Secured Party pursuant to this Section 3.3 The power of attorney granted
pursuant to this Section 313. is a power coupled with an interest and shall be
irrevocable until the Obligations are paid in full or otherwise satisfied in
full.



<PAGE>   4


                                    ARTICLE 4

                                     DEFAULT


        Section 4.1 Defaults, Events of Default, etc., Pledgor agrees that the
occurrence of the following, together with the expiration of any applicable
notice and/or cure period (if any), shall constitute an "Event of Default" under
this Agreement:

               (a)    If a default occurs under the Loan Agreement; or

        (b) If Pledgor fails faithfully to perform or observe any material
covenant or agreement herein to be performed by Pledgor and such failure has a
material adverse effect on the Collateral, and such failure continues for thirty
(30 days after notice thereof to Pledgor from Secured Party (provided that such
30-day period may be extended so long as such failure is capable of being cured
and Pledgor thereafter diligently pursues such a cure to Secured Party's
reasonable satisfaction); or

        (c) If any material representation or warranty of Pledgor contained in
this Agreement is in breach or is false when made or deemed made and such breach
or falsity has a material adverse effect on the Collateral; or.

        (d) In the event Secured Party shall cease to have a first priority
security interest in any of the Collateral (other than as a result of any action
or omission of Secured Party).

Section 4.2 Remedies Generally. Following the occurrence and during the
continuation of an Event of Default:

        (a) Secured Party may exercise all the rights and remedies of a secured
party under the Code.

        (b) Pledgor recognizes that Secured Party may be unable to effect a sale
to the public of all or part of the Collateral by reason of a certain
prohibitions or restrictions in federal or state securities laws and regulations
(herein collectively called the "Securities Laws"), or the provisions of other
federal and state laws, regulations or rulings, but may be compelled to resort
to one or more sales to a restricted group of purchasers who will be required to
agree to acquire the Collateral for their own account, for investment and not
with a view to the further distribution or resale thereof without restriction.
Pledgor agrees that any sale (s) so made may be at prices and other terms less
favorable to Pledgor than if the Collateral were sold to the public, and that
Secured Party has no obligation to delay the sale of the Collateral for
period(s) of time necessary to permit the issuer thereof to register the
Collateral for sale to the public under any of the Securities Laws. Pledgor
agrees that negotiated sales whether for cash or credit made under the



<PAGE>   5



foregoing circumstances shall not be deemed for that reason not to have been
made in a commercially reasonable manner. Pledgor shall cooperate with Secured
Party and shall satisfy any requirements under the Securities laws applicable to
the sale or transfer of the Collateral.

                                    ARTICLE 5

                                   DEFINITIONS

        The following terms shall have the respective meanings set forth below;

        "Agreement" shall mean this Pledge Agreement, by and among Pledgor and
Secured Party, as the same may from time to time be amended or supplemented.


        "Code" shall mean the California Uniform Commercial Code.

        "Collateral" shall have the meaning given in Section 1.1

        "Obligations" shall have the meaning given in Section 1.1.

        "Pledged Collateral" shall have the meaning given in Section 1.1(a).

        "Pledged Collateral Payments" shall have the meaning given in Section
         3.2(a)

        "Pledgor" shall mean National Insurance Group.

        "Secured Party" shall mean Imperial Bank.


                                    ARTICLE 6

                                  MISCELLANEOUS


        Section 6.1 No Waiver; Remedies. No failure on the part of Secured Party
to exercise, and no delay in exercising any right hereunder shall operate as a
waiver thereof; nor shall any single or partial waiver or exercise of any right
hereunder preclude any other or further waiver or exercise thereof or the waiver
or exercise of any other right. Except as express provided herein, the remedies
herein provided are cumulative and not exclusive of any remedies provided by
law.

        Section 6.2 Termination.

        (a) Upon the full and final payment or other satisfaction of all
Obligations and upon termination of all of Pledgor's other obligations under
the Loan Documents and the obligations of Pledgor hereunder, the liens and
security interests created by this Agreement and by the Other Assurances shall
terminate



<PAGE>   6



forthwith and all right, title and interest of Secured Party in and to the
Collateral shall revert to Pledgor, and its successors and assigns.

        (b) Upon the termination of Secured Party's liens and security interests
and the release of the Collateral, Secured Party will promptly (I) execute and
deliver to Pledgor such documents as Pledgor shall reasonably request to
evidence the termination of such security interest and the release of the
Collateral, and (ii) deliver or cause to be delivered to Pledgor all property of
Pledgor then held by Secured Party or any agent thereof, all without
representation or warranty by Secured Party (other than acknowledgment of
receipt of repayment) and with no recourse to Secured Party.

        (c) This Agreement shall terminate when the liens and security interests
granted hereunder have terminated and the Collateral has been released.

        Section 6.3 Successors and Assigns. This Agreement shall bind and inure
to the benefit of the respective successors and assigns of each of the parties;
provided; however, that Pledgor may not assign this Agreement or any rights or
duties hereunder without Secured Party's prior written consent and any
prohibited assignment shall be absolutely void. No consent to an assignment by
Secured Party shall release Pledgor from its obligations hereunder. Secured
Party may assign this Agreement and its rights and duties hereunder and no
consent or approval by Pledgor is required in connection with any such
assignment. Secured Party reserves the right to sell, assign, transfer,
negotiate, or grant participation in all or any part of, or any interest in
Secured Party's rights and benefits hereunder. In connection with any such
assignment or participation, Secured Party may disclose all documents and
information which Secured Party now or hereafter may have relating to Pledgor or
Pledgor's business, provided that such recipient executes a confidentiality
agreement reasonably satisfactory to Pledgor.

        Section 6.4 Attorney's Fees. If any party to this Agreement shall bring
any action or proceeding for any relief against the other, declaritory or
otherwise, arising out of this Agreement, the losing party shall pay to the
prevailing party a reasonable sum for attorney's fees and costs incurred in
bringing or defending such action or proceeding and/or enforcing any judgment
granted therein, all of which shall be paid whether or not such action or
proceeding is prosecuted to final judgment. Any judgment or order entered in
such action or proceeding shall contain a specific provision providing for the
recovery of attorneys' fees and costs, separate from the judgment, incurred in
enforcing each judgment. The prevailing party shall be determined by the trier
of fact based upon an assessment of which party's major arguments or positions
taken in the proceedings could fairly be said to have prevailed over the other
party's major arguments or positions on major disputed issues.



<PAGE>   7



        Section 6.5 Section Headings. Headings and numbers have been set forth
herein for conveniences only. Unless the contrary is compelled by the context,
everything contained in each section applies equally to this entire Agreement.

        Section 6.6 Interpretation. Neither this Agreement nor any uncertainty
or ambiguity herein shall be construed or resolved against Security Party or
Pledgor, whether under any rule of construction or otherwise. On the contrary,
this Agreement has been reviewed by all parties and shall be construed and
interpreted according to the ordinary meaning of the words used so as to fairly
accomplish the purposes and intentions of all parties hereto.

        Section. 6.7 Severability of Provisions. Each provision of this
Agreement shall be severable from every other provision of this Agreement for
the purpose of determining the legal enforceability of any specific provision.

        Section 6.8 Amendments in Writing. This Agreement can only be amended by
a writing signed by both Secured Party and Pledgor.

        Section 6.9 Counterparts. This Agreement may be executed I any number of
Counterparts and by different parties on separate counterparts, each of which,
when executed and delivered, shall be deemed to be an original, and all of
which, when taken together, shall constitute but one and the same Agreement.

        Section 6.10 Integration. This Agreement, together with the other Loan
Documents, reflects the entire understanding of the parties with respect to the
transactions contemplated hereby and shall not be contradicted or qualified by
any other agreement, oral or written, before the date hereof,

        Section 6.11 Notices. Unless otherwise provided in this Agreement, all
notices or demands by any party relating to this Agreement or any other Loan
Document shall be in writing and (except for financial statements and other
informational documents which may be sent by first-class mail, postage prepaid)
shall be personally delivered or sent by registered or certified mail, postage
prepaid, return receipt requested, or by prepaid telex, telefacsimile, or
telegram (with messenger delivery specified) to Pledgor or to Secured Party, as
the case may be, at its address set forth in the Loan Agreement.

      The parties hereto may change the address at which they are to receive
notices hereunder, by notice in writing in the foregoing manner given to the
other. All notices or demands sent in accordance with this Section, shall be
deemed received on the earlier of the date of Actual receipt or three (3) days
after the deposit thereof in the mail.

        Section 6.12 CHOICE OF LAW.



<PAGE>   8



        THE VALIDITY OF THIS AGREEMENT, ITS CONSTRUCTION, INTERPRETATION, AND
ENFORCEMENT, AND THE RIGHTS OF THE PARTIES HERETO WITH RESPECT TO ALL MATTERS
ARISING HEREUNDER OR RELATED HERETO SHALL BE DETERMINED UNDER, GOVERNED BY, AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF CALIFORNIA, WITHOUT GIVING
EFFECT TO ITS CONFLICT OF LAWS PRINCIPLES.

        IN WITNESS WHEREOF, Pledgor and Secured Party have caused this Agreement
to be executed by their duly authorized representatives as of the day and year
first above written.

                                   Imperial Bank



                                   By:   /s/ JOSEPH J. MCCARTHY
                                        ---------------------------------------
                                   Name:     Joseph J. McCarthy
                                   Title:    Vice President


                                   National Insurance Group


                                   By:   /s/ ROBERT P. BARBAROWICZ
                                        ---------------------------------------
                                   Name:     Robert P. Barbarowicz
                                   Title:    E.V.P. General Counsel & Secretary


                                   National Insurance Group



                                   By:   /s/ ROBERT J. LELIEUR
                                        ---------------------------------------
                                   Name:     Robert J. Lelieur
                                   Title:    V.P. Treasurer & Controller