Article ID: 976051
In an audio or a video conferencing session, the Microsoft Office Communicator 2007 R2 screen freezes intermittently for several seconds. This problem occurs if Office Communicator 2007 R2 is connected to a Tandberg video conferencing system by a long-distance Multiprotocol Label Switching (MPLS) wide area network (WAN) link.
Note This issue may also occur between two Communicator 2007 R2 clients.
To resolve this issue, apply the following update:
(http://support.microsoft.com/kb/972884/ )Description of the update for Communicator 2007 R2: Oct 2009