New computer, CS just exits to desktop

So I just got my new computer, (core 2 duo 6600, 2 gigs ram, geforce 7900) and whenever i join a CS server, I see one frame of the game and then it exits to the desktop with no error messages or anything.

also, i tried just regular Halfe-Life deathmatch, and the game stayed open, but unless i was looking at the menu (by either hitting esc, or the tilde key) i couldn't see anything. as in, the game looked perfectly normal if i was looking at the console, but as soon as i went back to just the game it froze up until i went back to the console.


any ideas?