When the game loses focus (clicking to something else) there's about a 75% chance it will not recover when the focus is returned. There seems to be some stuck loop going on that isn't breaking when focus is returned. Wish I knew more, but I'd have to see the code to narrow it down.
Even with the last EXE patch it still has issues. Also, there's an odd "refresh/redraw" of the game window that seems like the game reopening the game window quickly every so many minutes.
Windows 7 x64, Core i7 920, 18GB ram