When multiple users join a conversation by using Microsoft Lync 2013, the users may encounter the following issues:
A user cannot start desktop or application sharing.
When a graphics adapter crashes or changes dynamically during a desktop or application sharing session, the viewers’ screens stop updating for the sharing session.
Lync 2013 crashes when a user shares their desktop or an application.
To resolve this issue, install the following update:
2889860 September 2014 update for Lync 2013 (KB2889860)