Random Shutting down

I have been dealing with a problem with my computer for 1-2 months now. I cannot seem to find the solution and have tried many things. Every now and again, Almost at set intervals (Happens a almost same interval for certain days then switches the next), My Video card (NVidia 295 GTX)'s Red Light turns on. This light is normaly Green. This normaly means a power failure or temp shutdown. The computer stays on though, The fans still keep going but it seems everything else shuts down. I have found that my temps seem to be fine at the time of shutdown.

Specs:
Ultra X3 (1000W)
NVidia 295
Intel i7 950 CPU
8GB (4X2GB) 1600MHz DDR3 (Default at 1600)
Some generic HDD and CD Drive

I have had the 295 and the PSU for a while now (1-2 years). The CPU is pretty new though. Does anyone have anything I can try or anything that may be going wrong? I don't have a spare PSU that will work in my system. (It's very power hungry)