My Alienware keeps shutting down and restarting.

Hey Guys

Any help would be appreciated. My Alienware Area 51 Intel core I7 x980 @ 3.33mhz running Windows 7 64 keeps shutting down and restarting. At first I thought it was power surges so put a Powerware uninterrupted power supply on her, but she is still doing it? Any thoughts on what it may be? It has the lastest bios and microsoft upgrades. Running Mcaffe Suite. It is still under warrenty as It is only 8 months old. Any thoughts would be appreciated.

Cheers