VS 2012 hangs when closing solution

Whenever I close my solution, VS hangs up and I have to kill it. In Task Manager it shows up as"not responding" and uses 25% of CPU. We get the same behavior on exit.  This happens on several machines. (MSDNPremium 11.0.50727.1 RTMREL)

This is a fairly large solution that we've ported from VS2010. The only nonstandard thing I can see is that we're using Ankh/SVN.

Any suggestions on how to track this down?

Thanks