EXHIBIT 10.20
 
AMENDMENT TO GUARANTY

    Amendment dated as of December 17, 2007 (this "Amendment:") to that certain
Guaranty dated as of Decmeber 23, 2006 (the "Guaranty" by Gerald J. Burnett and
by Gerald J. Burnett and Marjorie J. Burnett, as Trustees for The Gerald J.
Burentt and Marjorie J. Burnett Revocable Trust (collectively, the "Guarantor"),
in favor of JPMorgan Chase Bank, N.A. (the "Bank").

For value received, the parties hereby agree as follows:
 1. Unless otherwise agreed in writing, notices may be given to the Bank and the
    Guarantor at their telecopier numbers (confirmed by telephone to their
    telephone numbers) or addresses listed below, or such other telecopier (and
    telephone) number or addresses communicated in writing by either party to
    the other.  Notices to the Bank are effective on receipt.
    
 2. Notwithstanding anything to the contrary set forth herein, for purpose of
    this Guaranty the Facilities of the Borrower guaranteed shall be limited to
    those arisign under and in connection with the Revolving Promissory Note
    (Libor/Prime) dated as of December 23, 2006 by the Borrower in favor of the
    Bank in the maximum principal amount of $10,000,000, as amended from time to
    time (the "Note") or any other "Facility Document" (as defined in the Note),
    together with every renewal, extension, amendment, modification,
    substitution and /or replacement thereof, each of which together with this
    Guaranty and any other writing or record evidencing, supporting, securing or
    delivered in connnection with the foregoing shall be considered a Ficility
    Document for purposes of this Guaranty.
    
 3. Clause (b) of the second sentence of the paragraph of the Guaranty titled
    "Guaranty Absolute" is hereby ameded by inserting the words "(any change in
    the value of any collateral or failure of the Bank to monitor the value of
    any collateral)" immediately following the words "release or non-perfection
    of any collateral".
    
 4. The Guaranty, as amended by this Amendment, remains in full force and
    effect.
    
 5. The Amendment shall be governed by and construed in accordance with the laws
    of the State of New York, without regard to conflicts of lawsa principles.
    
 6. This Amendment may be executed in any number of counterparts and by
    different parties hereto in separate counterparts, each of which shall be
    deemed to be an original, but all of which taken together shall constitute
    one in the same instrument.
    
    
    IN WITNESS WHEREOF, the parties have caused this Amendment to be duly
    executed and delivered as of the date first above written.
    
    
    JPMorgan Chase Bank, N.A.
    By:           J.P. Morgan Trust Company, N.A.
    
    
    
    
    
    
    By:       /s/ Nancy A.
    Sheppard                                               
                Nancy A. Sheppard
                Managing Director
    
    Address for notices to the Bank:
    
    
    JPMorgan Chase Bank, N.A.
    Private Bank Credit
    Attn: Patricia DeLeo
    345 Park Avenue, Floor 04
    New York, NY 10154-0004
    Telecopier:  (212) 464-2531
    Telephone:  (212) 464-1883
    
    
    With a courtesy copy to
    
    
    JPMorgan Chase Bank, N.A.
    Attn:  Nancy A. Sheppard
    560 Mission Street, 12th floor
    San Francisco, CA 94105
    Telecopier:  415 315 8272
    Telephone:  415 315 8285
    
    
    
    /s/ Gerald J. Burnett
    Gerald J. Burnett
    
    
    Address for notices:
    
    202 Camino  Al Lago
    Atherton, CA 94027
    Telecopier:  650.322.2060
    Telephone: 650.322.2060
    
    
    
    Gerald J. Burnett and Marjorie J. Burnett, as Trustee for The Gerald J.
    Burnett and Marjorie J. Burnett Revocable Trust
    
    
    
                 /s/ Gerald J. Burnett
    By:       Gerald J. Burnett
                   
                 /s/ Marjorie J. Burnett
    By:      Marjorie J. Burnett                                               
                          
    Address for notices:
    
    
    202 Camino  Al Lago
    Atherton, CA 94027
    Telecopier:  650.322.2060
    Telephone: 650.322.2060