Using 1.1b2 you get the following error-message whenever you ALT-TAB out of Smokin'-Guns and back in:
Com_QueueEvent: overflow
Additionally Mouse-Input within Smokin-Guns ain't working anymore (you ain't able to look to the left or to the right). And outside the game, you ain't able to move mouse at all.
I played with a previous 1.1-version so far, where those problems didn't exist yet.
There's another description of this problem from someone else:
http://bugzilla.icculus.org/show_bug.cgi?id=4334
/quit