I've been having this problem recently where my game crashes in the middle of a game or in a lobby. I remember this happening a few months ago but it only happened a few times, I am getting this issue almost everytime a play black ops 2 and I am finding the game unplayable. What usually happens is that I get into a game and after a few minutes the game freezes and I have to open up task manager on my second monitor to close the game. My computer runs relativly cool with my CPU running around 30-40C and GPU running 40C most of the time when in game. If you need my computer specs here they are:
Asus gtx 660
Geforce 337.50 driver (BETA)
I found a youtube video of someone having the exact same issue as me. Skip near the end to see the problem that I am experiencing.