<Page>

                                                                   EXHIBIT 10.31

                                 LOAN AGREEMENT
                                                                   SEPT. 1, 1993
                              SAN DIEGO, CALIFORNIA

PREAMBLE: This Note is a consolidation of all amounts loaned by GERALD G. LOEHR
TRUST ("Holder") to Aurora Technologies Corporation ("Aurora"), a California
Corporation. This Note cancels all loans made by GERALD G. LOEHR TRUST prior to
this date and all loan guarantees prior to this date by any and all Aurora
directors to other Aurora directors.

Aurora promises to pay to the GERALD G. LOEHR TRUST a resident of RANCHO SANTA
FE, CA 92067 ("Holder") at P.O. BOX 675207 the principal sum of
ONE-HUNDRED-NINETY THOUSAND DOLLARS ($190,000.00), with interest on such
principal sum from the date of this Note, as more fully set forth below.

         1.  PAYMENTS.  Principal and interest under this Note shall be
paid as follows.

             1.1.  Commencing on the first day of the month following the
date of executing this agreement and continuing until February 1, 1996,
interest only shall be paid at the rate of eight percent (8%) per annum.
Thereafter principal and interest at the rate of 1.5% above the interest rate
of a thirty-year U.S. treasury note maturing February 1, 2026, shall be paid
in such equal monthly payments that the entire indebtedness shall be paid off
on February 1, 2001.

             Any or all of this Note may be prepaid without penalty. Any
prepayments shall first be applied to unpaid interest and then to principal.
Aurora agrees not to prepay any amount on this Note unless equal amounts are
paid on the other two similar loan agreements of this same date between Aurora
and JACK F. BUTLER and CLINTON L. LINGREN.

         2.  MANNER OF PAYMENTS.  All payments by Aurora under this Note shall
be made in lawful money of the United States of America without set-off,
deduction or counterclaim of any kind whatsoever.

         3.  COMMERCIAL PURPOSES.  Aurora acknowledges that the loan evidenced
by this Note is obtained for business or commercial purposes and that the
proceeds of such loan will not be used primarily for personal, family, household
or agricultural purposes.

         4.  NOTE WAIVERS.  Aurora waives presentment, demand, protest, notice
of demand and dishonor.

         5.  GOVERNING LAW.  This Note shall be governed by and construed in
accordance with the laws of the State of California.

         6.  VENUE AND JURISDICTION.  For purposes of venue and jurisdiction,
this Note shall be deemed made and to be performed in San Diego, California.


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         7.  TIME OF ESSENCE.  Time and strict and punctual performance are of
the essence with respect to each provision of this Note.

         8.  ATTORNEY'S FEES. The prevailing party to this Note shall be
entitled to recover from the unsuccessful party to this Note all costs,
expenses, and actual attorney's fees relating to or arising from the enforcement
or interpretation of, or any litigation, arbitration or mediation relating to or
arising from, this Note.

         9.  MODIFICATION.  This Note may be modified only by a contract in
writing executed by the party to this Note against whom enforcement of such
modification is sought.

         10. HEADINGS.  The headings of the Paragraphs of this Note have been
included only for convenience, and shall not be deemed in any manner to modify
or limit any of the provisions of this Note, or be used in any manner in the
interpretation of this Note.

         11. PRIOR UNDERSTANDINGS.  This Note contains the entire agreement
between the parties to this Note with respect to the subject matter of this
Note, is intended as a final expression of such parties' agreement with respect
to such terms as are included in this Note, is intended as a complete and
exclusive statement of the terms of such agreement, and supersedes all
negotiations, stipulations, understandings, agreements, representations and
warranties, if any, with respect to such subject matter, which precede or
accompany the execution of this Note.

         12. INTERPRETATION.  Whenever the context so requires in this Note, all
words used in the singular shall be construed to have been used in the plural
(and vice versa), each gender shall be construed to include any other genders,
and the word "person" shall be construed to include a natural person, a
corporation, a firm, a partnership, a joint venture, a trust, an estate or any
other entity.

         13. PARTIAL INVALIDITY.  Each provision of this Note shall be valid and
enforceable to the fullest extent permitted by law. If any provision of this
Note or the application of such provision to any person or circumstance shall,
to any extent, be invalid or unenforceable, the remainder of this Note, or the
application of such provision to person or circumstances other than those as to
which it is held invalid or unenforceable, shall not be affected by such
invalidity or unenforceability, unless such provision or such application of
such provision is essential to this Note.

         14. SUCCESSORS-IN-INTEREST AND ASSIGNS.  This Note shall be binding
upon and shall inure to the benefit of the successors-in-interest and assigns
of each party to this Note. Nothing in this Paragraph shall create any rights
enforceable by any person not a party to this Note, except for the rights of
the successors-in-interest and assigns of each party to this Note, unless
such rights are expressly granted in this Note to other specifically
identified persons.

         15. WAIVER.  Any waiver of a default under this Note must be in
writing and shall not be a waiver of any other default concerning the same or
any other provision of this Note. No delay or omission in the exercise of any
right or remedy shall impair such right or remedy or be


                                       2
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construed as a waiver. A consent to or approval of any act shall not be
deemed to waive or render unnecessary consent to or approval of any other or
subsequent act.

GERALD G. LOEHR TRUST                     AURORA TECHNOLOGIES CORPORATION
                                          A California corporation

By:  /s/ Gerald G. Loehr  Trustee    By:   /s/ Jack F. Butler       9/1/93
   --------------------------------     ----------------------------------
     Gerald G. Loehr                       Jack F. Butler, President


                                     By:   /s/ Clinton L. Lingren   9-1-93
                                        ----------------------------------
                                           Clinton L. Lingren, Secretary


                                       3
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                           AMENDMENT TO LOAN AGREEMENT

         THIS AMENDMENT TO LOAN AGREEMENT (the "Amendment") dated as of May 13,
1994 amends the Loan Agreement dated as of September 1, 1993 by and between
AURORA TECHNOLOGIES CORPORATION, a California corporation, with principal
offices at 7408 Trade Street, San Diego, California 92121-2410 (the "Company"),
and GERALD G. LOEHR, ("Lender"), as amended by the Addendum to Loan Agreement
dated as of January 1, 1994, February 17, 1994 and April 14, 1994 (collectively,
the "Original Agreement").

         WHEREAS, Lender together with JACK F. BUTLER, and CLINTON L. LINGREN,
collectively (the "Founders"), have individually entered into loan agreements
with the Company which provide for the Company to repay to the Founders
principal totaling $735,000 and interest thereon;

         WHEREAS, the Company and Kingsbury Capital Partners, L.P. ("Kingsbury")
have entered into a Stock Purchase Agreement dated as of May 13, 1994, whereby
Kingsbury will provide additional financing to the Company in exchange for
Series A Preferred Stock of the Company, pursuant to which the Company has
agreed to enter into this Amendment with Lender to amend the terms of the
Original Agreement by the terms set forth below;

         NOW, THEREFORE, in consideration of the promises and of the mutual
provisions and obligations hereinafter set forth, the parties hereto agree as
follows:

         1.  PAYMENTS.  Principal and interest under this Amendment shall be
paid as follows.

                  1.1  Interest shall be paid quarterly. The simple rate of
interest shall be six and thirty-five hundredths percent (6.35%) per annum.
Notwithstanding any provision of this Amendment, it is the intent and agreement
of the parties that in the event any interest specified herein is found to
violate any applicable law or regulation, this Amendment shall be construed or
deemed amended so that the interest is adjusted to the extent necessary to
comply with such applicable law or regulation.

                  1.2  Payment of principal shall not become due until the later
of (i) March 31, 1999 or (ii) March 31 of the year immediately following the
first year in which the Company's cash provided by operations is greater than
zero as shown on the Company's audited statement of cash flows for such year.
Subject to certain exceptions to payment provided herein, the principal shall be
paid to Lender in twelve (12) equal quarterly installments, the first such
payment to be made within forty-five (45) days of the initial due date and
subsequent quarterly installments to be paid within forty-five (45) days of the
end of each subsequent quarter. The Company shall make payment of quarterly
installments to Lender in equal proportion to the amounts paid to the other
Founders, and shall not make payment of any portion of Lender's principal before
similar payment to other Founders. Notwithstanding anything to the contrary
herein, the aggregate amount of the quarterly installments to principal paid to
Lender and the other Founders shall not exceed fifty percent (50%) of the
Company's cash provided by operations as shown on the Company's unaudited
statement of cash flows for the prior quarter, in


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which event, any unpaid amounts of principal shall be carried forward and
subsequent quarterly installments shall be adjusted accordingly to account for
the principal carried forward.

         2.  Except as set forth herein, there have been no other amendments to
the Original Agreement and all terms and conditions thereof shall remain in full
force and effect.

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

         4.  No waiver or modification of the terms of this Amendment shall be
valid unless in writing, signed by both parties to this Amendment.

         5.  This Amendment shall be governed by and construed in accordance
with the laws of the State of California, irrespective of its choice of law
provisions.

         IN WITNESS WHEREOF, the parties have caused this Amendment to be
signed in duplicate by their duly authorized representatives. Entered into as
of the day and year first above written.

                                      AURORA TECHNOLOGIES CORPORATION


                                      By       /s/ Jack Butler
                                         ---------------------------------
                                      Title    President
                                            ------------------------------


                                               Gerald G. Loehr
                                      ------------------------------------
                                      By       /s/ Gerald Loehr, Trustee
                                         ---------------------------------
                                      Title
                                            ------------------------------


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AURORA TECHNOLOGIES CORPORATION
--------------------------------------------------------------------------------
                                    7408 TRADE STREET - SAN DIEGO, CA 92121-2410
                                             (619) 549-4545 - FAX (619) 549-7714


                           ADDENDUM TO LOAN AGREEMENT

This ADDENDUM amends the Agreement between GERALD G. LOEHR and Aurora
Technologies Corporation ("Aurora") dated September 1, 1993 ("Original
Agreement") to allow additional amounts to be loaned to Aurora from time to
time, with the principal sum being increased accordingly. The rates of interest
and all terms and conditions contained in the Original Agreement will apply to
the loans and new principal amounts.

Loans will be considered valid and new principal amounts established when
properly recorded and accepted by the named Aurora officials below.

<Table>
<S>                         <C>                            <C>>
    1.  1/1/94              $20,000.00                     $210,000.00
        -----------------   -------------------            -----------------------
        Date                Amount Loaned                  New Principal Balance

        Loaned by:          Accepted for Aurora
                            Technologies Corporation by:

        /s/ Gerald Loehr    /s/ Jack F. Butler             /s/ Clinton L. Lingren
        -----------------   -------------------            -----------------------
                            Jack F. Butler                 Clinton L. Lingren
                            President                      Secretary

    2.  2/17/94             $25,000.00                     $235,000.00
        -----------------   -------------------            -----------------------
        Date                Amount Loaned                  New Principal Balance

        Loaned by:          Accepted for Aurora
                            Technologies Corporation by:

        /s/ Gerald Loehr    /s/ Jack F. Butler             /s/ Clinton L. Lingren
        -----------------   -------------------            -----------------------
                            Jack F. Butler                 Clinton L. Lingren
                            President                      Secretary

    3.  4/14/94             $10,000.00                     $245,000.00
        -----------------   -------------------            -----------------------
        Date                Amount Loaned                  New Principal Balance

        Loaned by:          Accepted for Aurora
                            Technologies Corporation by:

        /s/ Gerald Loehr    /s/ Jack F. Butler             /s/ Clinton L. Lingren
        -----------------   -------------------            -----------------------
                            Jack F. Butler                 Clinton L. Lingren
                            President                      Secretary
</Table>