<Page>
                                                                   EXHIBIT 10.33


                                                                   SEPT. 1, 1993

                                 LOAN AGREEMENT

                              SAN DIEGO, CALIFORNIA

PREAMBLE: This Note is a consolidation of all amounts loaned by JACK F. BUTLER
("Holder") to Aurora Technologies Corporation ("Aurora"), a California
Corporation. This Note cancels all loans made by JACK F. BUTLER 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 JACK F. BUTLER a resident of RANCHO SANTA FE, CA
("Holder") at P.O. BOX 1333 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 GERALD G. LOEHR
TRUST 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.

         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.

                                       -1-

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         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 persons 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 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/ Jack F. Butler             By:    /s/ Clinton L. Lingren      9-1-93
    -----------------------------      --------------------------------------
     Jack F. Butler                        Clinton L. Lingren, Secretary


                                       -2-
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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 7406 Trade Street, San Diego, California 92121-2410 (the
"Company"), and JACK F. BUTLER, ("Lender"), as amended by the Addendum to
Loan Agreement dated a8 of January 1, 1994, February 17, 1994 and April 14,
1994 (collectively, the "Original Agreement").

         WHEREAS, Lender together with CLINTON L. LINGREN, and GERALD G.
LOEHR, 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 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.

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         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 F. Butler
                                         -----------------------------------
                                      Title President
                                            --------------------------------


                                      Clinton L. Lingren
                                      --------------------------------------
                                      By /s/ Clinton L. Lingren
                                         -----------------------------------
                                      Title
                                            --------------------------------

<Page>

AURORA TECHNOLOGIES CORPORATION
--------------------------------------------------------------------------------
                                    7408 TRADE STREET - SAN DIEGO. CA 92121-2410
                                             (619) 549-4645 - FAX (619) 549-7714


                           ADDENDUM TO LOAN AGREEMENT

This ADDENDUM amends the Agreement between JACK F. BUTLER 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.  1/1/99                $20,000.00                      $210,000.00
    -------------------   -------------------             -----------------------
    Date                  Amount Loaned                   New Principal Balance

    Loaned by:            Accepted for Aurora
                          Technologies Corporation by:

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