I'm having issues with my 6600GT!
Basically, when I have it plugged into the power supply, the computer freezes for 3-10 seconds, goes to a black screen for 3-5 seconds and then goes back to normal. This can happen every minute or two, and is really annoying. However, when I unplug it from the power supply, I get the warning message about low power/low performance on startup, however I don't get any lockups.
Now I thought it might be my power supply, but the power supply is 400W with 18A on the +12V, and from what I've read, that is more than enough.
Anyone got any ideas?