In a Microsoft Lync 2010 environment, the Office Communicator Object Model (OCOM) API needs to call additional subscription to stop polling subscriptions.
To resolve this issue, install the following cumulative update:
2551268 Description of the cumulative update package for Lync 2010: May 2011
After you install this cumulative update, the OCOM API can remove subscriptions without calling additional subscription.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.