GPU smoking; memories incandescent

I have a big GPU problem. It's a ATI4870, brand new system. Everything worked fine (games on max settings etc), and then I ran folding@home. After about 5 minutes, the system completely shuts down. The system doesn't restart at all, so I guess it's a power failure (standard symptoms, but I have a high end thermaltake 750W toughpower PPU...)anyways...

-I unplug the power, replug, power on, and I hear some loud sizzling, followed by some smoke and burn smells. I immediately power down. After powering back up everything works fine.

-The next day, it happens again. Thinking I'm wiser, I press the power button while the system is off to empty all latent electricity. so everything should be fine. When I power on, I hear the same deep frying, followed by a puff of smoke coming from the graphics card. The system works fine the next day.

I tried installing all the newest drivers. The computer works fine. I played UT3 at max for about 3 hours, no pb. I try, F@H, and it crashes on me again...

-THIS time, I unplug all the power on the graphic card, so I don't burn it. Get this: the instant I turn on the card, one of the little memory modules (? those 1.5mm*2mm black blocks) immediately turns red, smoking and melting! I power down, and the module is indeed quite fried. All this, with the card un-plugged.

-Thinking the damage is done (it is), I try powering up again. This time, I have time to see another memory turn red and smoke, but much slower. I immediately power off.

Now, every time I power on, that one little memory turns red and smokes. I don't dare just leaving it turned on to see what happens

What is going on!?!?!?
I paid this system expensive, and I'm not exactly rich. I can't even tell if this is really a GPU or PPU problem. The GPU seems fine till I use F@H on it, and I also tested the PPU at a vendor's place. I'd return the components, but what is causing the problem here? does anyone have any idea? How can I tell which component is faulty? I'd hate changing my GPU (it's under warranty), only to burn a new one!

Also, I don't have onboard video, so I can't run any tests without the card, and my PC case doesn't have a speaker, so I can't hear sysem messages

For info: I have not done ANY overclocking or anything fancy. here are the components:
-GPU Gainward golden sample 4870
-Gigabyte GA-MA-X790 motherboard
-Thermaltake 750 Watts toughpower
Thanks

Have you Check your GPU on others PC?

You Dont do Anything With your System. and i think Possibly the damage may have been done to your system. this is possibly due to voltage fluctuation and maybe created to due to overvoltage. just what you can do is Show it to any Authorised Serviceman if it in not in warranty.if it is then send it back to service center for repair. possibly this seem to be Smps Fault. or Loose Wiring

I think you need to buy a voltage stabilizer so that you can make stable power supply bcoz it is clearly seems to be damage due to abnormal voltage variations. Better is take the advantage of warranty period or consult a hardware specialist. Good luck

I only have this computer, so I don't have any spare parts to interchange and test. I'm going to return the GPU, but I wonder if I should return the PSU...?