I have to agree with Esk for what she posted. Could also be your GPU is on it's way out as well. Have you tried to shut down some of the "extra" processes running in the background that aren't needed like iTunes helper, acro reader and any other type of non needed "start-up" processes? Afterall, you don't need adobe running in the background when your not using it.

Run a few tests like Esk suggested and see what fails if anything. Hopefully not only because it would suck but if it DOES prove something is wrong, you can fix it.

Edit: Yes I know those other processes shouldn't be that intense on your i7. I'm just asking/suggesting to hopefully minimize the extra garbage to have the system run a bit "cleaner" during game play.