Consider the following scenario. You install a Microsoft Lync 2010 client and Outlook on a computer that is using Internet Explorer 9. You click a Join Online meeting link and successfully join a meeting. In this scenario, the Internet Explorer 9 window does not close automatically.
To resolve this issue, install the following cumulative update:
2514979 Description of the cumulative update package for Lync Server 2010, Web Components Server: November 2011