EXHIBIT 10.17

GUARANTY

GUARANTY dated as of December 23, 2006 made by the undersigned (individually, or
if more than one, collectively, the “Guarantor”) in favor of JPMorgan Chase
Bank, N.A., and/or any of its subsidiaries or affiliates (individually or
collectively, as the context may require, the “Bank”).

PRELIMINARY STATEMENTS:  The Bank has entered, or may from time to time enter,
into agreements or arrangements with Avistar Communications Corporation, a
Delaware corporation (the “Borrower”), providing for credit extensions or
financial accommodation to the Borrower of any kind whatsoever including,
without limitation, the making of loans, advances or overdrafts, whether or not
secured, discount or purchase of notes, securities or other instruments or
property, creation of acceptances, issuance or confirmation of letters of
credit, guaranties or indemnities, entering into foreign exchange or precious
metals contracts or interest rate or currency swap or protection agreements,
entering into any other derivative transactions under any ISDA Master Agreement
or similar agreements between the Bank and the Borrower, or any other kind of
lease, contract or agreement under which the Borrower may be indebted to the
Bank in any manner (all of the foregoing agreements or arrangements being the
“Facilities” and any writing or record evidencing, supporting, securing, or
delivered in connection with a Facility, including but not limited to this
Guaranty, and including as may subsequently be renewed, extended, amended, 
modified, substituted and/or replaced, being a “Facility Document”).

THEREFORE, in order to induce the Bank to extend credit or give financial
accommodation under the Facilities, the Guarantor agrees (and if more than one,
jointly and severally agrees) as follows:

Guaranty of Payments.  For value received and in consideration of the Facilities
extended by the Bank the Guarantor unconditionally and irrevocably guarantees to
the Bank (a) performance and observance of every agreement and condition
contained in any Facility Document to be performed or observed by the Borrower,
and (b) payment of all sums now owing or which may in the future be owing by the
Borrower under the Facilities, when the same are due and payable, whether on
demand, at stated maturity, by acceleration or otherwise, and whether for
principal, interest, fees, expenses, indemnification or otherwise (the
“Liabilities”).  The Liabilities include, without limitation, interest accruing
after the commencement of a proceeding under bankruptcy, insolvency or similar
laws of any jurisdiction at the rate or rates provided in the Facility
Documents.

This Guaranty is a guaranty of payment and performance and not of collection
only.  The Bank shall not be required to exhaust any right or remedy or take any
action against the Borrower or any other person or entity or any collateral. 
The Guarantor agrees that, as between the Guarantor and the Bank, the
Liabilities may be declared to be due and payable for the purposes of this
Guaranty notwithstanding any stay, injunction or other prohibition which may
prevent, delay or vitiate any declaration as regards the Borrower and that in
the event of a declaration or attempted declaration, the Liabilities shall
immediately become due and payable by the Guarantor for the purposes of this
Guaranty.

The Guarantor shall pay the Liabilities by the seventh (7th) day on which
commercial banks are not authorized or required to close in New York City (a
“Banking Day”) after the Bank’s demand for payment thereof (or if such demand is
accompanied by notice from the Bank, or the Bank thereafter delivers notice,
that the value of collateral securing the Liabilities is less than the amount of
the Liabilities, on the second (2nd) Banking Day after delivery of such notice)
(the “Due Date”).  Upon the Bank’s making demand for payment of the Liabilities
but prior to the Due Date, the Guarantor shall have the right (but not the
obligation) to execute and deliver to the Bank a note sale agreement
substantially in the form of Exhibit A hereto (the “Loan Sale Agreement”)
together with payment of the “Note Purchase Price” (as defined therein) in
immediately available funds, whereupon the obligations of the Guarantor
hereunder shall terminate (but subject to reinstatement as provided below).

Guaranty Absolute.  The Guarantor guarantees that the Liabilities shall be
performed and paid strictly in accordance with the terms of the Facilities.  The
liability of the Guarantor under this Guaranty is absolute and unconditional
irrespective of:  (a) any change in the amount, time, manner or place

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of payment of, or in any other term of, all or any of the Facility Documents or
Liabilities, or any other amendment or waiver of or any consent to departure
from any of the terms of any Facility Document or Liability; (b) any release or
amendment or waiver of, or consent to departure from, any other guaranty or
support document, or any exchange, release or non-perfection of any collateral,
for all or any of the Facility Documents or Liabilities; (c) any present or
future law, regulation or order of any jurisdiction (whether of right or in
fact) or of any agency thereof purporting to reduce, amend, restructure or
otherwise affect any term of any Facility Document or Liability; (d) without
being limited by the foregoing, any lack of validity or enforceability of any
Facility Document or Liability; and (e) any other defense, setoff or
counterclaim whatsoever (in any case, whether based on contract, tort or any
other theory) with respect to the Facility Documents or the transactions
contemplated thereby which might constitute a legal or equitable defense
available to, or discharge of, the Borrower or a guarantor.

Guaranty Irrevocable.  This Guaranty is a continuing guaranty of all Liabilities
now or hereafter existing under the Facilities and shall remain in full force
and effect until payment in full of all Liabilities and other amounts payable
under this Guaranty and until the Facilities are no longer in effect or, if
earlier, when the Guarantor has given the Bank written notice that this Guaranty
has been revoked; provided that any notice under this Section shall not release
the Guarantor from any Liability, absolute or contingent, existing prior to such
notice.  Such notice shall be effective only after the Bank’s actual receipt of
the notice at its address set forth below, and the Bank shall have had a
reasonable time to act upon such notice at each of its offices or departments
responsible for the Facilities.

Reinstatement.  This Guaranty shall continue to be effective or be reinstated,
as the case may be, if at any time (i) any payment of any of the Liabilities is
rescinded or must otherwise be returned by the Bank on the insolvency,
bankruptcy or reorganization of the Borrower or otherwise, all as though the
payment had not been made or (ii)  the Loan Sale Agreement  shall be held
invalid or unenforceable in whole or in any part..

Subrogation.  The Guarantor shall not exercise any rights against the Borrower
which it may acquire by way of subrogation, by any payment made under this
Guaranty or otherwise, until all the Liabilities have been paid in full and the
Facilities are no longer in effect.  If any amount is paid to the Guarantor on
account of subrogation rights under this Guaranty at any time when all the
Liabilities have not been paid in full, the amount shall be held in trust for
the benefit of the Bank and shall be promptly paid to the Bank to be credited
and applied to the Liabilities, whether matured or unmatured or absolute or
contingent, in accordance with the terms of the Facilities.

Subordination.  Without limiting the Bank’s rights under any other agreement,
any liabilities owed by the Borrower to the Guarantor in connection with any
extension of credit or financial accommodation by the Guarantor to or for the
account of the Borrower, including but not limited to interest accruing at the
agreed contract rate after the commencement of a bankruptcy or similar
proceeding, are hereby subordinated to the Liabilities, and such liabilities of
the Borrower to the Guarantor, if the Bank so requests, shall be collected,
enforced and received by the Guarantor as trustee for the Bank and shall be paid
over to the Bank on account of the Liabilities but without reducing or affecting
in any manner the liability of the Guarantor under the other provisions of this
Guaranty.

Representations and Warranties.  The Guarantor represents and warrants that:

(a)                   this Guaranty constitutes the legal, valid and binding
obligation of the Guarantor, enforceable against the Guarantor in accordance
with its terms, except as the enforcement hereof and thereof may be limited by
bankruptcy, insolvency, or other similar laws affecting the enforcement of
creditors’ rights generally and subject to the applicability of general
principles of equity;

(b)                   the execution, delivery and performance by the Guarantor
of this Guaranty and all other documents contemplated hereby or thereby, do not
and will not (i) conflict with or constitute a breach of, or default under, or
require any consent under, or result in the creation of any lien, charge or
encumbrance upon the property or assets of the Guarantor pursuant to any other
agreement or instrument (other than any pledge of or security interest granted
in any collateral pursuant to any Facility Document) to which the Guarantor is a
party or is bound or by which its properties may be bound or affected; or

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(ii) violate any provision of any law, rule, regulation (including, without
limitation, Regulation U of the Federal Reserve Board), order, writ, judgment,
injunction, decree, determination or award presently in effect having
applicability to the Guarantor;

(c)                   no consent, approval or authorization of, or registration,
declaration or filing with, any governmental authority or other person or entity
is required as a condition to or in connection with the due and valid execution,
delivery and performance by the Guarantor of this Guaranty;

(d)                   there are no actions, suits, investigations or proceedings
pending or threatened at law, in equity, in arbitration or by or before any
other authority involving or affecting:  (i)  the Guarantor that, if adversely
determined, are likely to have a material adverse effect on the prospects or
condition of the Guarantor; (ii) any material part of the assets or properties
of the Guarantor or any part of the collateral (if any) under any Facility
Document; or (iii) any of the transactions contemplated in this Guaranty.  There
are currently no material judgments entered against the Guarantor and the
Guarantor is not in default with respect to any judgment, writ, injunction,
order, decree or consent of any court or other judicial authority, which default
is likely to have or has had a material adverse effect on the prospects or
condition of the Guarantor;

(e)                   in executing and delivering this Guaranty, the Guarantor
has (i) without reliance on the Bank or any information received from the Bank
and based upon such documents and information it deems appropriate, made an
independent investigation of the transactions contemplated hereby and the
Borrower, the Borrower’s business, assets, operations, prospects and condition,
financial or otherwise, and any circumstances which may bear upon such
transactions, the Borrower or the obligations and risks undertaken herein with
respect to the Liabilities; (ii) adequate means to obtain from the Borrower on a
continuing basis information concerning the Borrower and the Bank has no duty to
provide to the Guarantor any such information; (iii) full and complete access to
the Facility Documents and any other documents executed in connection with the
Facility Documents; (iv) not relied and will not rely upon any representations
or warranties of the Bank not embodied herein or any acts heretofore or
hereafter taken by the Bank (including but not limited to any review by the Bank
of the affairs of the Borrower), and (v) determined that this Guaranty will
benefit the Guarantor directly or indirectly;

(f)                    in the event that the Guarantor is a partnership, limited
liability partnership, corporation or limited liability company, the Guarantor
also represents and warrants (i) that it is duly organized, validly existing and
in good standing under the laws of the jurisdiction of its incorporation or
organization, (ii) that it has all requisite power and authority to execute,
deliver and perform its obligations under this Guaranty, and (iii) that the
execution, delivery and performance of this Guaranty is in furtherance of its
organizational purposes, and has been presented to and approved by its partners,
directors, shareholders or members, as applicable; and

(g)                   in the event that the Guarantor is a trust, the Guarantor
also represents and warrants that (i) it is a duly constituted and validly
existing trust, (ii) the Guarantor has delivered to the Bank a true, complete
and accurate copy of the agreement pursuant to which it has been organized and
all amendments and modifications thereto, and (iii) the trustees of the
Guarantor signing this Guaranty have the legal capacity and full power and
authority to execute, deliver, and perform their obligations under, and to bind
the Guarantor to perform its obligations under, this Guaranty, and to execute
and deliver any and all documents and instruments in connection herewith.

Defaults.  Each of the following is an event of default hereunder:

(a)                   The Guarantor (i) shall fail to pay when due any of its
indebtedness (including, but not limited to, indebtedness for borrowed money) or
any interest or premium thereon in an aggregate amount of at least five hundred
thousand dollars ($500,000) or (ii) the Guarantor shall default or otherwise
fail to perform any agreement to which the Guarantor is party or by which it is
bound which results in the holder(s) of indebtedness having the right, whether
or not exercised, to accelerate the maturity thereof in an aggregate amount of
at least five hundred thousand dollars ($500,000);

(b)                   (i) the Guarantor is involved in a proceeding which may
result in a forfeiture of all or a substantial part of the Guarantor’s assets or
(ii) a final, non-appealable judgment is entered against the Guarantor for the
payment of in an aggregate amount of at least two million dollars ($2,000,000);

(c)                   there is, in the opinion of the Bank, a material adverse
change in the business, prospects or financial condition of the Guarantor;

(d)                   without the prior written consent of the Bank, the
Guarantor incurs or permits to exist (i) any debt for borrowed money other than
debt for borrowed money owing to the Bank or

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listed on the Guarantor’s financial statement dated April 20 2006 (the
“Financial Statement”) and any refinancing of such debt or (ii) other debt to
the extent that the total amount thereof when added together with the total
amount of the Borrower’s guarantees and contingent liabilities referred to in
clause (ii) of the immediately following paragraph (e) is less than or equal to
seven million dollars ($7,000,000); and

(e)                   the Guarantor guarantees or otherwise becomes contingently
liable for the debts or other obligations of any entity other than (i) any such
guaranty or contingent obligation shown on the Financial Statement and
(ii) guarantees and contingent obligations incurred after the date of the
Financial Statement to the extent that the total amount thereof when added
together with the total amount of debt referred to in clause (ii) of the
immediately preceding paragraph (d) is less than or equal to seven million
dollars ($7,000,000).

Remedies Generally.  The rights, powers and remedies granted to the Bank in this
Guaranty are cumulative and in addition to any rights, powers and remedies to
which the Bank may be entitled either by operation of law or in equity or
pursuant to any other document or instrument delivered or from time to time to
be delivered to the Bank in connection with the Facilities.

Setoff.  The Guarantor agrees that, in addition to (and without limitation of)
any right of setoff, banker’s lien or counterclaim the Bank may otherwise have,
the Bank shall be entitled, at its option, to offset balances (general or
special, time or demand, provisional or final) held by it for the account of the
Guarantor at any of the Bank’s offices, in U.S. dollars or in any other
currency, against any amount payable by the Guarantor under this Guaranty which
is not paid when due (regardless of whether such balances are then due to the
Guarantor), in which case it shall promptly notify the Guarantor thereof;
provided that the Bank’s failure to give such notice shall not affect the
validity thereof.

Formalities.  The Guarantor waives presentment, notice of dishonor, protest,
notice of acceptance of this Guaranty or incurrence of any Liability and to the
extent not prohibited by applicable law any other formality with respect to any
of the Liabilities or this Guaranty.

Amendments and Waivers.  No amendment or waiver of any provision of this
Guaranty, nor consent to any departure by the Guarantor therefrom, shall be
effective unless it is in writing and signed by the Bank, and then the waiver or
consent shall be effective only in the specific instance and for the specific
purpose for which given.  No failure on the part of the Bank to exercise, and no
delay in exercising, any right under this Guaranty shall operate as a waiver or
preclude any other or further exercise thereof or the exercise of any other
right.

Expenses.  The Guarantor shall reimburse the Bank on demand for all costs,
expenses and charges (including without limitation fees and charges of external
legal counsel for the Bank and costs allocated by its internal legal department)
incurred by the Bank in connection with the preparation, performance or
enforcement of this Guaranty.  The obligations of the Guarantor under this
Section shall survive the termination of this Guaranty.

Assignment.  This Guaranty shall immediately be binding on, and shall inure to
the benefit of the Guarantor, the Bank and their respective heirs, successors
and assigns; provided that the Guarantor may not assign or transfer its rights
or obligations under this Guaranty.

Captions.  The headings and captions in this Guaranty are for convenience only
and shall not affect the interpretation or construction of this Guaranty.

Governing Law, Waiver of Jury Trial, Etc.  THIS GUARANTY SHALL BE GOVERNED BY
AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT
REGARD TO THE CONFLICT OF LAWS PRINCIPLES, AND WITH THE LAWS OF THE UNITED
STATES OF AMERICA AS APPLICABLE.  THE GUARANTOR CONSENTS TO THE NONEXCLUSIVE
JURISDICTION AND VENUE OF THE STATE OR FEDERAL COURTS LOCATED IN THE CITY OF NEW
YORK.  SERVICE OF PROCESS BY THE BANK IN CONNECTION WITH ANY SUCH DISPUTE SHALL
BE BINDING ON THE GUARANTOR IF SENT TO THE GUARANTOR BY REGISTERED MAIL AT THE
ADDRESS

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SPECIFIED BELOW OR AS OTHERWISE SPECIFIED BY THE GUARANTOR FROM TIME TO TIME. 
THE GUARANTOR WAIVES ANY RIGHT THE GUARANTOR MAY HAVE TO JURY TRIAL IN ANY
ACTION RELATED TO THIS GUARANTY OR THE TRANSACTIONS CONTEMPLATED HEREBY AND
FURTHER WAIVES ANY RIGHT TO INTERPOSE ANY COUNTERCLAIM RELATED TO THIS GUARANTY
OR THE TRANSACTIONS CONTEMPLATED HEREBY IN ANY SUCH ACTION.  TO THE EXTENT THAT
THE GUARANTOR HAS OR HEREAFTER MAY ACQUIRE ANY IMMUNITY FROM JURISDICTION OF ANY
COURT OR FROM ANY LEGAL PROCESS (WHETHER FROM SERVICE OR NOTICE, ATTACHMENT
PRIOR TO JUDGMENT, ATTACHMENT IN AID OF EXECUTION OF A JUDGMENT, EXECUTION OR
OTHERWISE), THE GUARANTOR HEREBY IRREVOCABLY WAIVES SUCH IMMUNITY IN RESPECT OF
ITS OBLIGATIONS UNDER THIS GUARANTY.

Integration; Effectiveness.  This Guaranty alone sets forth the entire
understanding of the Guarantor and the Bank relating to the guarantee of the
Liabilities and constitutes the entire contract between the parties relating to
the subject matter hereof and supersedes any and all previous agreements and
understandings, oral or written, relating to the subject matter hereof.  This
Guaranty shall become effective when it shall have been executed and delivered
by the Guarantor to the Bank.  Delivery of an executed signature page of this
Guaranty by telecopy shall be effective as delivery of a manually executed
signature page of this Guaranty.

The rest of this page is intentionally blank.

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IN WITNESS WHEREOF, the Guarantor has caused this Guaranty to be duly executed
and delivered as of the date first above written.

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

 

 

 

 

 

With a courtesy copy to

 

 

 

 

 

JPMorgan Chase Bank, N.A.

 

 

Attn: Nancy A. Sheppard

 

 

560 Mission Street, 12th floor

 

 

San Francisco, CA 94105

 

 

 

 

 

/s/ Gerald J. Burnett

 

 

 

Gerald J. Burnett

 

 

 

 

 

Address for notices:

 

 

 

 

 

 

 

 

Gerald J. Burnett and Marjorie J. Burnett , as Trustee for

 

 

The Gerald J. Burnett and Marjorie J. Burnett Revocable Trust

 

 

 

 

 

 

 

 

By:

  /s/ Gerald J. Burnett, trustee

 

 

 

Gerald J. Burnett

 

 

 

 

 

By:

  /s/ Marjorie J. Burnett, trustee

 

 

 

Marjorie J. Burnett

 

 

 

 

 

 

 

 

 

 

 

Address for notices:

 

 

 

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Exhibit A

FORM OF NOTE SALE AGREEMENT

A-1

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