You cannot join an Audio/Video conference and you hear a fast busy tone when you try to join the conference by using Lync 2010
Content provided by Microsoft
Applies to: Lync Server 2010 Standard EditionLync Server 2010 Enterprise Edition
When you try to join an Audio/Video conference by using Microsoft Lync 2010, you hear a fast busy tone and your attempt to join the Audio/Video conference fails. Additionally, Monitoring Server indicates several 7025 events that contain the following error message:
reason="Internal server error creating media for user"; component="Audio Video Conferencing Server"; OriginalPresenceState="0"; CurrentPresenceState="0"; MeInsideUser="Yes"; ConversationInitiatedBy="0"; SourceNetwork="0"; RemotePartyCanDoIM="No"
Note This issue disappears after you restart the Audio/Video Conferencing Multipoint Conferencing Unit (MCU). However, this issue occurs again after the Audio/Video Conferencing MCU is running for some time.
This issue occurs because the 64-bit tick count is implemented incorrectly. Therefore, conferences are cleaned up too early by the garbage collection in the Media Processor.
To fix this problem, install the following cumulative update:
2449497 Description of the update package for Lync Server 2010, Web Components Server: January 2011
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.