Article ID: 2489823 - View products that this article applies to.
Consider the following scenario:
This issue occurs because the RTAudio narrowband decoder cannot process the ringback tones that certain European gateways use.
To resolve this issue, install the following cumulative update:
(http://support.microsoft.com/kb/2501722/ )Description of the cumulative update package for Communicator 2007 R2: March, 2011
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.