Consider the following scenario. You use Microsoft Lync 2010 to start a conference that includes more than 200 users. You try to initiate an application-sharing session. In this scenario, you cannot share an application unless the Application Sharing multipoint control unit service is restarted.
Note This issue occurs if the conference is hosted in a Lync Server 2010 Standard Edition pool. If the conference is hosted in a Lync Server 2010 Enterprise Edition pool, application sharing works after several minutes delay.
This issue occurs because an access violation occurs in the Application Sharing multipoint control unit.
To resolve this issue, install the following cumulative update:
2514975 Description of the cumulative update for Lync Server 2010, Conferencing Server: April 2011
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.