Couple things. Its been my experience a video card gremlin is usually one of three things: Drivers, power, temp.
Does it do it on a known good system? This will help on drivers.
Does the problem rig have a big enough PSU? The GX2 were thirsty for their class. Take their min specs and DOUBLE it. You will see milisecond peaks that are wayyyy above its spec. If you dont have enough PSU to handle SLI cards... you probably dont have enough to handle the GX2... so if you got a piddly little 500 PSU... its the PSU.
Temperatures. Run furmark or some other stress test. What are the temps? Does it lock up. If so... AND its OOW, yank the heatsink and reapply TIM, then increase fan speed profile.
also the guide is
The firmware utility
hope that helps
for forceware don't forget about filehippo that fat bastard seems to have lots of old files