EX58-Extreme start up failure

System:
Brand New

Gigabyte EX58-Extreme
Core i7 920
3 x 2 Corsair DDR3 1600 Mhz RAM
Asus Geforce 9400 GS (interim card awaiting GTX 295 delivery)
2 x WD 1tb Black 7200 RPM HDD's
Pioneer DVR 218 DVD writer
Coolermaster Haf 932 case
Coolermaster V8 CPU cooler
Corsair HX 850 PSU
Windows 7

Installed all the components, used thermal paste, RAM chips in slots 2/4/6 (from left as you look at them)
Booted system, installed Win 7. then spent about an hour installing office and the like. Installed utorrent and commenced a torrent download and went to bed. Got up in the morning and the PC was off.
Turned it on and it booted into windows and shut down before loading gadgets.
It will not turn on anymore.

Have tried the following:
Reset CMOS
Removed CMOS Battery
Unplugged Power and re-inserted it
Removed and relocated all RAM
Removed and reloacted the Graphics cards.
Removed all external fan connectors
Unplugged MB power (both of them) and re-inserted
Removed all MB connectors and re-inserted

Power requires complete external power down prior to attempting a re-power.
Power switches (both internal and front panel power) are activated and system powers up for approximately 1/2 a second and then powers down. Mains power is required to be reset to allow another attempt at power on.

Basically I cannot even get into the BIOS. The system does not beep. The only sound is a click and the fan start sequence before loss of power.

I will try using only single RAM sticks when I get home from work.

Thanks in advance.
Brom

Thanks... No problems there at all. I have completely dismantelled the MB and rechecked everything... then swapped PSU's over and it seems to be working now. So it looks like a brand new Corsair HX850 PSU is kaput.. will watch and see and replace the defective PSU tomorrow.

Well it is confirmed that the PSU was defective. My shop replaced it with no problems, however they too were suprised... it happens.

Cheers.

She loves the 850.. no issues, just a bad one thats all
with what Im running, I needed at least 699 watts.