New Rig POST issues

So here's the deal, i recently build my new rig and everything ran fine for a couple of days until this morning.

I left my PC on overnight to download my Steam games so when i woke up this morning and realized it wasn't running i was already wondering. Then i proceeded to try and Power the system on but all that happened was my Fans spinning for about half to a second before the system would shut down again. After a couple tries i noticed that both fan headers on the bottom of the board seem to not work. I then proceeded to take the thing apart again and ran just the motherboard with a stick of ram, cpu and my h100i still mounted. It would POST but then i realized that i forgot to plug the 12V rail for the cpu back in so i shut the system down and plugged it in, resulting in the system shutting down after about a second again.

So it's clear that at least one of either my Motherboard, CPU or PSU are broken and have to be RMA'd but i'm not sure which one it is. Any hints would be appreciated.

EDIT: Full specs on my profile page

If you can, get your hands on another PSU and test with that. The fact that it isn't posting with the CPU power connector in shows there maybe some issues with it.

If you do get hold of another PSU and the same problem occurs, it is the motherboard. It is very rare for a CPU to be die so quickly, unless your cooler wasn't mounted correctly.

The cpu was around 50°C while playing The Witcher 2 and Guild Wars 2 and idling at about 29°C to 31°C. Thanks for the response i'll try to find a psu to test and will keep this thread updated.

Allright i just tried a different psu and the same thing happened. I certainly didn't expect a sabertooth to break this fast. Maybe i just got a bad sample. Thanks for the help i'll rma the board tomorrow.

I finally got my replacement board today and the exact same things happen. I take it i owe Asus an apology and need to get my cpu replaced. *sigh* 

maybe your psu is broken? is your H100i still working? it could have failed and killed your CPU.

i already tried a different psu with the old board. is there a way to test if the pump of the h100i is working without being able to POST?