In case you missed it, there was an important update to the Microsoft Lync for Mac 2011 client last week. Update 14.0.1 addresses issues with signing into Office 365 and with the client closely unexpectedly during sign-in.
I have seen many Office 365 forum postings about the Lync for Mac 2011 client not being . . . → Read More: Microsoft Lync for Mac 2011 Update