Computer turns on and then turns off in half second

Hey guys,

I was using my computer last night perfectly until it froze, I shut down the computer and went to sleep. Next morning I tried to turn it on but when I pressed the power button, the led fans went up but turned off immediately after half second. Then I began my troubleshooting by removing all components and installing it again but still no boot. I took out the mobo and mounted the system out of the case.

System configuration:
EVGA X58 SLI LE motherboard
Intel Core i7 920 2.66
Ocz 6gb ddr3 1600mhz
3x GTX260 in three-way SLI
WD velociraptor 10k 300gb
Corsair TX850w psu

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Troubleshoot configuration out of the case:
EVGA X58 SLI LE
Intel Core i7 920 2.66 w/ stock fan
Ocz 2gb ddr3 1600mhz (1 stick)
1x GTX260
WD velociraptor 10k 300gb
Corsair TX850w psu

When the system is off, there is a blue LED (indicating that the mobo is receiving power) and a yellow LED (it means that the memory slot is functional)

When the system is on, a green LED comes up (system is on) but nothing else. I mean, after pressing the onboard power button, there is no post, no boot, no beeps, no error codes in the LCD (this mobo includes an integrated LCD that shows error codes if there is something preventing the system from booting). I noticed that I'm not able to turn off the system by pushing down the power button for 5 seconds (the only way to turn it off is disconnecting the psu).

Any suggestions?