Are you over clocking it? Download some decent Overclocking software and check the MHz for the Memorary, might be set to high!
Nope. I haven't touched the clocks or voltages at all. It's a fresh card, right out of the box. It crashes *after* I stop mining (i.e. when I hit 'q' to quit). cgminer displays "Thread 0 disabled" and then the computer locks up, and has to be restarted manually. Thanks!