Crash after being in the game for a few minutes

[d_train2k]

The game crashes after being in a mission for about a minute or two. Sometimes the whole game crashes out right, but the most common crash i've been experiencing is that the visuals go first (i.e. screen goes black) but I can still hear the sound effects and the game seems to accept inputs (can hear guns fire when I pull the trigger). Then shortly after the game crashes properly. Sounds like it a may be graphics card issue, but I'm not sure what to do about it. I'm running in DX 11 so I'm not sure if I have to manually set it to DX 10 or not. Anyway, here are my specs and thank you in advance for any help.

Q6600 at 2.4ghz
GTX 560
Windows 7