You have Microsoft Lync 2010 Phone Edition installed on one of the following telephones:
You connect a computer that has Lync 2010 installed to the PC port on the telephone.
You try to receive a multicast stream on the computer.
In this scenario, packet loss occurs. For example, when you view a multicast video stream, the video output is choppy.
This issue occurs because the telephone device driver is handled incorrectly.
To resolve this issue, install the appropriate cumulative update for the telephone that you are using:
For HP 4110 and HP 4120 telephones
2672743 Description of the cumulative update for Lync 2010 Phone Edition for HP 4110 and HP 4120: February 2012
For Polycom CX500, Polycom CX600, and Polycom CX3000 telephones
2672349 Description of the cumulative update for Lync 2010 Phone Edition for Polycom CX500, Polycom CX600, and Polycom CX3000: February 2012
For Aastra 6721ip and Aastra 6725ip telephones
2672352 Description of the cumulative update for Lync 2010 Phone Edition for Aastra 6721ip and Aastra 6725ip: February 2012
The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.