After the Lync 2013 upgrade I made at my company in December, we have been having problems with multiparty IM and voice calls, as well as with the Lync whiteboard feature and other stuff.
We develop software that integrates with Lync (http://www.blueposition.com/lync and http://www.busylight.com/), so our production Lync installation should really be working properly, but I haven’t had the time to look into the problem in details, and no amount of googling the error messages helped.
Today however, my colleague had to debug a problem to one of our software products, that only occurred when the user was in a voice conference, so the Lync issue had to be solved – otherwise he had no way of reproducing the software problem.