On the video card question, I had similar issues back in the day with a Radeon 5870 when I using particular power cables coming from my power supply.
Turns out, the 1000W PSU I had used more than one rail and it had issues driving the load that the GPU demanded. Once I distributed the load across different rails the issues went away.
But yeah after RMAing the card and doing a clean install, you'll have to look elsewhere like a bad mobo/ram/psu etc.
w00tazn's comments