Article ID: 2586041 - View products that this article applies to.
When you start two instances of a Microsoft Lync 2010 Group Chat client at the same time, a race condition occurs. Additionally, this causes the Lync 2010 Group Chat client to crash.
To resolve this issue, install the following cumulative update:
(http://support.microsoft.com/kb/2636065 / )Description of the cumulative update for Lync 2010 Group Chat client: November 2011