Alright, so I built a custom tower about 2 years ago, everything was working beautifully until yesterday. I was messing around with Blender 3D when my computer shut off on it's own during a render. I try turning it back on, but no go. It responds with a single twitch from the PSU and System fan, as well as a quick flash from the LEDs.
I took it apart and tested it with nothing but the Motherboard and PSU. Same response. I noticed that if I unplug the 8 pin 12v ATX cable and leave the larger ATX cable plugged in it will run a little longer(about 1 fan rotation), before quitting. Repeatedly, after about 4 seconds it will turn on again, and shut off just as quick.
My first thought was the PSU, so I brought it in to have it tested at our local computer store. The man there concluded that the PSU is good. So I'm guessing it's my motherboard... fun.
My question is, with all this said, what possibly could have happened, and is there something I may have missed in my testing.
Motherboard - Gigabyte GA-P55A-UD3
CPU - Intel Core i7-860 2.8GHz Quad-Core Processor
PSU - Sunbeam PSU-ECO750-US-BL 750W ATX12V
Memory - G.SKILL 4GB (2 x 2GB) 240-Pin DDR3 2200
GPU - HIS H567FO1G Radeon HD 5670 1GB 128-bit DDR3 PCI Express 2.1 x16