Video (and computer) freezing

I plugged my computer to the UPS, but the computer still freezes every once in a while, for 10-20 seconds at a time. It happens not only when I'm watching TV, but playing videos, too. I'm guessing these three reasons:

• power surges
• insufficient power supply, or
• video card overheating

I'm hoping it's not a defective card coz sending it back to Taiwan would be a bitch.

Just another item in the long list of things that fuck up for absolutely no reason. Story of my life.