While the behavior you are describing could certainly be caused by a bad video card, it could also be caused by a CPU, RAM, Power Supply, or heat problem. Here are some suggestions to test for each possibility:
* CPU: If the processor is having problems, then you should be able to cause the same failure when you run the CPU tests.
* RAM: As with the CPU, just run some memory tests to see if you can get the system to fail.
* Power Supply: Unfortunately, there is no way to use software to detect if the Power Supply is having problems. If you have a Service Center Premier Kit we include a Power Supply Tester to check the voltages.
* Heat: If the computer is overheating, the system could cut power to avoid damage to the CPU and motherboard. A good place to start is just by checking your case for dust, and making sure that it is getting adequate airflow (do the fans work, are the vents blocked by carpet, etc.).
Of course, if you are only seeing this failure when you test the graphics card, then your assumption is most likely correct. Please let me know if you have any other questions or issues.
Thanks,
Kris