I haven't tried the old power supply on another computer, but I will in the next hour. The memory is fine, the cpu is fine, and the motherboard is fine because we booted it up with an older videocard and it worked. We cant even get into the bios. I will have you guys know though that, on my video card I replaced the thermal pads with arctic silver 5, which did nothing but worked awesome. I also replaced the thermal pads on the north and south bridge with arctic silver 5 too.
Everything worked for a month though. And power is still getting to the motherboard. It's just like my computer is a vegetable.
The Silverstone PSU and the 8800GTX.
If that Silvestone works fine on the other computer, then it is likely that the problem is your 8800GTX.
However, I would try putting everything back together how it was when it worked before. Try that one more time before you make any RMAs.