Left 4 Dead 2 Mouse Freezing

Anyone else having mouse freezing issues since the latest patch? I just tried playing a few rounds with a friend and each time we start another segment for a given level (part 2 of Death Toll), I find that I have no mouse control whatsoever in the safe room. Even when I alt-tab to the desktop, the mouse is still unresponsive. The only thing that fixes it is a reboot. Anyone else? I can't find anything on the Googs...