Assume that in a Microsoft Lync Server 2010 environment you install the Lync Server 2010 cumulative updates that were released in February 2012. When a user clicks the Join online meeting link to join a Lync Online meeting, the web browser opens as expected. However, the client for Lync Server 2010 does not start.
To resolve this issue, install the following update:
2689846 Description of the update for Lync Server 2010: March 2012
To work around this issue, delete all temporary Internet files in the web browser on the client computer.