A memory leak occurs on a Microsoft Lync Server 2010, Web Conferencing server. In this situation, you have to manually restart the Web Conferencing service.
This issue occurs because some Centralized Conference Control Protocol related objects are not released in the Data Multipoint Control Unit (MCU) process.
To resolve this issue, install the following cumulative update:
2530592 Description of the cumulative update for Lync Server 2010, Web Conferencing server: April 2011
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.