Article ID: 2520139 - View products that this article applies to.
Consider the following Scenario:
Note This issue specifically occurs when you have a Session Initiation Protocol (SIP) certificate that is saved locally.
To resolve this issue, install the following cumulative update:
(http://support.microsoft.com/kb/2496325/ )Description of the cumulative update package for Lync 2010: April 2011
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.