Symptoms
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.
Cause
This issue occurs because the user must download and install a new JavascriptResourcehandler.ashx file on the client computer after the update is installed on the server. However, the file cannot be downloaded if a legacy JavascriptResourcehandler.ashx file in the cache has not expired. Therefore, the web browser cannot be redirected to the user's server pool.
Note When a user tries to join a Lync Online meeting, the JavascriptResourcehandler.ashx file must be downloaded from the Lync Server 2010 server. The expiration time of the file is one day.Resolution
To resolve this issue, install the following update:
2689846 Description of the update for Lync Server 2010: March 2012
Workaround
To work around this issue, delete all temporary Internet files in the web browser on the client computer.