We have received numerous reports that having Lync and Outlook 2011 open at the same time is causing one, or both, of the processes to use 100% of the CPU. This in turn causes Outlook to become unresponsive until you force quit either Outlook or Lync. Having the applications open separately does not cause a problem- only when they are both open at the same time.
To troubleshoot the problem, open Lync, go to Preferences/General and put a tick in "Turn on logging for troubleshooting". Restart Lync and then Open Outlook and Process Viewer. Work normally until Outlook freezes and you see in Process Viewer that the CPU use for Lync and/or Outlook has spiked.
Close (or force quit) Outlook and Lync and open Console Viewer.
In Console Viewer, under Files/~/Library/Logs open the Microsfot-Lync-0.log. Search the log for multiple (hundreds) of entries referencing the same e-mail address and having an "INFO" line of "FindOrCreateFakeContactModelForQuery"
Open Outlook and remove all references to the offending e-mail account. This includes contacts and any auto-complete entries.
To clear the auto-complete entries, open a new mail and start typing the user's name; a box should open that displays the e-mail address; to the right will be an "X". Click on the "X" to remove the entry.
Relaunch Outlook, open Lync and check that you no longer experience the high CPU problem.
When you are sure the problem has been resolved, make sure you turn off logging in Lync.