Yesterday Microsoft released a new Lync client update as part of the windows update. (its also available via a download here. http://support.microsoft.com/kb/2817621 there doesn’t seem to be much of information about the update apart from in also has the other patches within it..
The issue this patch is fixing is
– After you wake up the computer from hibernation mode, Lync 2013 becomes very slow and unusable.
Ive been running the update for a day now with no issues.