Not overclocked. I did take off the cover off my box at one point, and it did the same thing. It might be the PSU or the video card now that I think of it.
This is my power supply:http://www.newegg.com/Product/Product.asp?Item=N82E16817153039
My video card has been discontinued. This is the title, though:
POWERCOLOR X800GTO256MBDDR3 Radeon X800GTO 256MB 256-bit GDDR3 PCI Express x16 Video Card - Retail
The temperature does not exceed 45C. The probe is set within the heatsink.