Soooo Need help

Son was playing on computer and all of a sudden powered off no warning. After messing with it and checking everything I thought for sure it was the PSU.
What it does is as soon as you turn the psu to off then back to on everything starts to power up all fans kick and then within like 5 secs it just shuts completely back off and the only way to get it to even do that is if I turn power supply off or unplug it.
Green light on Motherboard even after it does this.
removed video card, checked all power connections even disconnected most that weren't essential same result. Oh I bouhgt a new PSU same result

MB is P5N32-E SLI
Mem Is Corsair Dominator 8500
Video is EVGA 8800gts

Help I am running out of ideas here

try pulling the mb out of the case and running it on a piece of cardboard. it sounds like your mb may be shorting into the case. be sure to doublecheck all of your fan connectors. particularly if you happen to have any 3-4pin adapters etc...
good luck!