A video call may fail when you try to start the video call by using Office Communicator on a computer that is running Windows Server 2008 or Windows Vista
When you try to start a video call by using Microsoft Office Communicator on a computer that is running Windows Server 2008 or Windows Vista, the video call may fail.
This problem may occur when a third-party legacy Transport Driver Interface (TDI) filter driver is installed on the computer. TDI filter drivers may be used by some antivirus software.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB946886.