Article ID: 2517729 - View products that this article applies to.
Consider the following scenario:
Note The Show Columns option is located under the View menu in a Group Chat client.
To resolve this issue, install the following cumulative update:
(http://support.microsoft.com/kb/2500446/ )Description of the update for Lync 2010 Group Chat Client: April 2011
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.