Asus p4p800-e power question

[captain_fink]

Built a computer about 4 months ago...

ASUS P4P800e-Deluxe
P4 478 pin 3.0ghz (northwood core)
1 gig RAM
6600gt
450 watt antec-smartpower psu

Its been running fine for about 3 months.

I turned it off about 2 weeks ago because I was going to try and sell it.

Found someone who's saying their interested, so I figured i'd fire it up, make sure it worked.

Now when i press the power button the power flashes... Front case lights and cd/dvd rom lights flash, fans spin in pulses.

I pulled all the power supply cables and jumped the green/black to see if its a burnt PSU. Its working fine, 12v/5v/3v.

Checked the switch in the front of the case, even used the reset button and no difference, still flashing the lights and sporadically whirling the fans.

Any idea what would cause this? There's nothing shorting out on the board that I can see, but its not the PSU or switch.

 

[captain_fink]

Unplugged everything but the vid card and hard disk, same flashing on/off.

Went to just the motherboard and when the power switch was pressed even the LED on the board would dim and light.

The PSU is good, checked it on a second system.

I'm still assuming its the motherboard.