# **EXHIBIT 10.17**

# **GUARANTY**

**GUARANTY** dated asof December 23, 2006 made by the undersigned (individually, or if morethan one, collectively, the “Guarantor”) in favor of JPMorgan ChaseBank, 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 mayfrom time to time enter, into agreements or arrangements with AvistarCommunications Corporation, a Delaware corporation (the “Borrower”),providing for credit extensions or financial accommodation to the Borrower ofany 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, issuanceor confirmation of letters of credit, guaranties or indemnities, entering intoforeign exchange or precious metals contracts or interest rate or currency swapor protection agreements, entering into any other derivative transactions underany ISDA Master Agreement or similar agreements between the Bank and theBorrower, or any other kind of lease, contract or agreement under which theBorrower may be indebted to the Bank in any manner (all of the foregoingagreements or arrangements being the “Facilities” and any writing orrecord evidencing, supporting, securing, or delivered in connection with aFacility, including but not limited to this Guaranty, and including as maysubsequently be renewed, extended, amended, modified, substituted and/or replaced, being a “Facility Document”).

**THEREFORE**, inorder to induce the Bank to extend credit or give financial accommodation underthe Facilities, the Guarantor agrees (and if more than one, jointly andseverally agrees) as follows:

**Guaranty of Payments**.  For value received and inconsideration of the Facilities extended by the Bank the Guarantorunconditionally and irrevocably guarantees to the Bank (a) performance andobservance of every agreement and condition contained in any Facility Documentto be performed or observed by the Borrower, and (b) payment of all sums nowowing 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 accelerationor 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 inthe Facility Documents.

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

The Guarantor shall pay the Liabilities by the seventh (7th) day onwhich 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 demandis accompanied by notice from the Bank, or the Bank thereafter delivers notice,that the value of collateral securing the Liabilities is less than the amountof the Liabilities, on the second (2nd) Banking Day after delivery of such notice) (the “DueDate”).  Upon the Bank’s making demandfor payment of the Liabilities but prior to the Due Date, the Guarantor shallhave the right (but not the obligation) to execute and deliver to the Bank anote sale agreement substantially in the form of Exhibit A hereto (the “LoanSale Agreement”) together with payment of the “Note Purchase Price” (as definedtherein) in immediately available funds, whereupon the obligations of theGuarantor hereunder shall terminate (but subject to reinstatement as providedbelow).

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

----

of payment of, or in any other term of, all or any ofthe Facility Documents or Liabilities, or any other amendment or waiver of orany consent to departure from any of the terms of any Facility Document orLiability; (b) any release or amendment or waiver of, or consent to departurefrom, any other guaranty or support document, or any exchange, release or non-perfectionof 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 ofright 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 orenforceability of any Facility Document or Liability; and (e) any otherdefense, setoff or counterclaim whatsoever (in any case, whether based oncontract, tort or any other theory) with respect to the Facility Documents or thetransactions contemplated thereby which might constitute a legal or equitabledefense available to, or discharge of, the Borrower or a guarantor.

**Guaranty Irrevocable**.  This Guaranty is a continuingguaranty of all Liabilities now or hereafter existing under the Facilities andshall remain in full force and effect until payment in full of all Liabilitiesand other amounts payable under this Guaranty and until the Facilities are nolonger in effect or, if earlier, when the Guarantor has given the Bank writtennotice that this Guaranty has been revoked; provided that any noticeunder this Section shall not release the Guarantor from any Liability, absoluteor contingent, existing prior to such notice. Such notice shall be effective only after the Bank’s actual receipt ofthe notice at its address set forth below, and the Bank shall have had areasonable time to act upon such notice at each of its offices or departmentsresponsible for the Facilities.

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

**Subrogation**.  The Guarantor shall not exercise any rightsagainst the Borrower which it may acquire by way of subrogation, by any paymentmade under this Guaranty or otherwise, until all the Liabilities have been paidin full and the Facilities are no longer in effect.  If any amount is paid to the Guarantor onaccount of subrogation rights under this Guaranty at any time when all theLiabilities have not been paid in full, the amount shall be held in trust forthe benefit of the Bank and shall be promptly paid to the Bank to be creditedand applied to the Liabilities, whether matured or unmatured or absolute orcontingent, in accordance with the terms of the Facilities.

**Subordination**.  Without limiting the Bank’s rights under anyother agreement, any liabilities owed by the Borrower to the Guarantor inconnection with any extension of credit or financial accommodation by theGuarantor to or for the account of the Borrower, including but not limited tointerest accruing at the agreed contract rate after the commencement of abankruptcy 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 theBank and shall be paid over to the Bank on account of the Liabilities butwithout reducing or affecting in any manner the liability of the Guarantorunder the other provisions of this Guaranty.

**Representations and Warranties**.  TheGuarantor represents and warrants that:

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

(b)                   the execution, delivery andperformance by the Guarantor of this Guaranty and all other documentscontemplated hereby or thereby, do not and will not (i) conflict with orconstitute a breach of, or default under, or require any consent under, orresult in the creation of any lien, charge or encumbrance upon the property orassets of the Guarantor pursuant to any other agreement or instrument (otherthan any pledge of or security interest granted in any collateral pursuant toany Facility Document) to which the Guarantor is a party or is bound or bywhich its properties may be bound or affected; or

2

----

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

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

(d)                   there are noactions, suits, investigations or proceedings pending or threatened at law, inequity, in arbitration or by or before any other authority involving oraffecting:  (i)  the Guarantor that, if adversely determined,are likely to have a material adverse effect on the prospects or condition ofthe Guarantor; (ii) any material part of the assets or properties of the Guarantoror 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 judgmentsentered against the Guarantor and the Guarantor is not in default with respectto any judgment, writ, injunction, order, decree or consent of any court orother judicial authority, which default is likely to have or has had a materialadverse effect on the prospects or condition of the Guarantor;

(e)                   in executingand delivering this Guaranty, the Guarantor has (i) without reliance on theBank or any information received from the Bank and based upon such documentsand information it deems appropriate, made an independent investigation of thetransactions contemplated hereby and the Borrower, the Borrower’s business,assets, operations, prospects and condition, financial or otherwise, and anycircumstances which may bear upon such transactions, the Borrower or theobligations and risks undertaken herein with respect to the Liabilities; (ii)adequate means to obtain from the Borrower on a continuing basis informationconcerning the Borrower and the Bank has no duty to provide to the Guarantorany such information; (iii) full and complete access to the Facility Documentsand any other documents executed in connection with the Facility Documents;(iv) not relied and will not rely upon any representations or warranties of theBank 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 theBorrower), and (v) determined that this Guaranty will benefit the Guarantordirectly or indirectly;

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

(g)                   in the eventthat 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 hasdelivered to the Bank a true, complete and accurate copy of the agreementpursuant to which it has been organized and all amendments and modificationsthereto, and (iii) the trustees of the Guarantor signing this Guaranty have thelegal capacity and full power and authority to execute, deliver, and performtheir obligations under, and to bind the Guarantor to perform its obligationsunder, this Guaranty, and to execute and deliver any and all documents andinstruments in connection herewith.

**Defaults.**  Each of the following is an event of defaulthereunder:

(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 premiumthereon in an aggregate amount of at least five hundred thousanddollars ($500,000) or (ii) the Guarantor shall default or otherwise failto perform any agreement to which the Guarantor is party or by which it isbound which results in the holder(s) of indebtedness having the right, whetheror not exercised, to accelerate the maturity thereof in an aggregate amount ofat least five hundred thousand dollars ($500,000);

(b)                   (i) theGuarantor is involved in a proceedingwhich 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 leasttwo million dollars ($2,000,000);

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

(d)                   without the prior writtenconsent of the Bank, the Guarantor incursor permits to exist (i) any debt for borrowed money other than debt forborrowed money owing to the Bank or

3

----

listed on the Guarantor’s financial statement datedApril 20 2006 (the “Financial Statement”) and any refinancing of such debtor (ii) other debt to the extent that thetotal amount thereof when added together with the total amount of theBorrower’s guarantees and contingent liabilities referred to inclause (ii) of the immediately following paragraph (e) is less thanor equal to seven milliondollars ($7,000,000); and

(e)                   the Guarantor guarantees or otherwise becomes contingently liable forthe debts or other obligations of any entity other than (i) any suchguaranty or contingent obligation shown on the Financial Statement**and (ii) guarantees and contingent obligationsincurred after the date of the Financial Statement to the extent that the totalamount thereof when added together with the total amount of debt referred to inclause (ii) of the immediately preceding paragraph (d) is less than orequal to seven milliondollars ($7,000,000).

**Remedies Generally**.  The rights, powers and remediesgranted to the Bank in this Guaranty are cumulative and in addition to anyrights, powers and remedies to which the Bank may be entitled either byoperation of law or in equity or pursuant to any other document or instrumentdelivered or from time to time to be delivered to the Bank in connection withthe Facilities.

**Setoff**.  The Guarantor agrees that, in addition to(and without limitation of) any right of setoff, banker’s lien or counterclaimthe Bank may otherwise have, the Bank shall be entitled, at its option, tooffset balances (general or special, time or demand, provisional or final) heldby 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 Guarantorunder this Guaranty which is not paid when due (regardless of whether suchbalances are then due to the Guarantor), in which case it shall promptly notifythe Guarantor thereof; provided that the Bank’s failure to give suchnotice shall not affect the validity thereof.

**Formalities**.  The Guarantor waives presentment, notice ofdishonor, protest, notice of acceptance of this Guaranty or incurrence of anyLiability and to the extent not prohibited by applicable law any otherformality with respect to any of the Liabilities or this Guaranty.

**Amendments and Waivers**.  No amendment or waiver of anyprovision of this Guaranty, nor consent to any departure by the Guarantortherefrom, 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 instanceand for the specific purpose for which given. No failure on the part of the Bank to exercise, and no delay inexercising, any right under this Guaranty shall operate as a waiver or precludeany other or further exercise thereof or the exercise of any other right.

**Expenses**.  The Guarantor shall reimburse the Bank ondemand for all costs, expenses and charges (including without limitation feesand charges of external legal counsel for the Bank and costs allocated by itsinternal legal department) incurred by the Bank in connection with thepreparation, performance or enforcement of this Guaranty.  The obligations of the Guarantor under thisSection shall survive the termination of this Guaranty.

**Assignment**.  This Guaranty shall immediately be bindingon, and shall inure to the benefit of the Guarantor, the Bank and theirrespective heirs, successors and assigns; provided that the Guarantormay not assign or transfer its rights or obligations under this Guaranty.

**Captions**.  The headings and captions in this Guarantyare for convenience only and shall not affect the interpretation orconstruction of this Guaranty.

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

4

----

**SPECIFIED BELOW OR ASOTHERWISE SPECIFIED BY THE GUARANTOR FROM TIME TO TIME.  THE GUARANTOR WAIVES ANY RIGHT THEGUARANTOR MAY HAVE TO JURY TRIAL IN ANY ACTION RELATED TO THIS GUARANTY OR THETRANSACTIONS CONTEMPLATED HEREBY AND FURTHER WAIVESANY RIGHT TO INTERPOSE ANY COUNTERCLAIM RELATED TO THIS GUARANTY OR THETRANSACTIONS CONTEMPLATED HEREBY IN ANY SUCH ACTION.  TO THE EXTENT THAT THE GUARANTOR HAS ORHEREAFTER MAY ACQUIRE ANY IMMUNITY FROM JURISDICTION OF ANY COURT OR FROM ANYLEGAL PROCESS (WHETHER FROM SERVICE OR NOTICE, ATTACHMENT PRIOR TO JUDGMENT,ATTACHMENT IN AID OF EXECUTION OF A JUDGMENT, EXECUTION OR OTHERWISE), THEGUARANTOR HEREBY IRREVOCABLY WAIVES SUCH IMMUNITY IN RESPECT OF ITS OBLIGATIONSUNDER THIS GUARANTY.**

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

**The rest of this page is intentionallyblank.**

5

----

**IN WITNESS WHEREOF, the Guarantorhas caused this Guaranty to be duly executed and delivered as of the date firstabove 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:**                                          |                                          |   |

 

6

----

Exhibit A

FORM OF NOTE SALEAGREEMENT

A-1

----