I built a gaming rig at the end of June, and at first I noticed every once in a while the mouse icon would stutter a lot when moving, then it'd be fine. Figured it was maybe just interference with bluetooth, as I'm using a Logitech MX 5500. However, last night while listening to music on iTunes, it started happening again and the audio would cut in and out with distortion until I just closed iTunes completely. The issue came up again today while using Steam and iTunes at the same time and it forced me to quit both programs, as it didn't look like it was going to stop. Now, I've just noticed it again while trying to play a flash video online.
Check your temps. Or maybe problematic video drivers. Try running in safe mode to check if it still happens. If it does maybe you have some hardware problem.
Video driver problems could be very possible. My temps always seem to be stable and my cpu is cooled by a Corsair H50 liquid cooler. Speedfan does not seem to correctly read the core temps, but I've never had a problem come up before telling me to shut down.