If you run OCS and Exchange 2007 UM together, you may notice the following error on the Exchange UM server:

The Telephony Manager declined a call with Call Id ‘dc792cb1-3c0e-4a97-a8dc-ec948047af15’ for the following reason in component telephony session: ‘The media description received from the remote SIP peer has an invalid content type ‘multipart/alternative’.’. 

While researching this event ID I found a blog on Technet that states it can be safely ignored, as this is expected behavior in OCS 2007 R2 / Unified Messaging integrated environments.