Keyboard and L/R mouse buttons quit working

[The Notorious T.A.F.T.]

I've been playing this ever since I got my new computer (a Lenovo Y400), and recently there was an update to the game. Now, I can't move my character or shoot/shove. Anybody else having these problems? I've switched back to L4D1 for the time being, which thankfully works just fine.

EDIT: I am running Windows 8 (unfortunately), if that might be part of it.