A little help here, please? ^_^

Hello,

I have a bit of a situation that I need some technical opinions on. Apologies ahead of time, if this is the incorrect area to post an issue like this.

I have a simple gaming machine:

Intel Extreme DX58SO Motherboard
Intel i7 920 Quad Core Proccessor
3x 2GB (6.0GB) Corsair XMS3 Series Memory
Galaxy GeForce GTS 250
BFG 550W PSU
Seagate 500GB SATA HDD
LG DVD-+RW/DL/CD-RW Burner

My problem:
I recently recieved a Warranty Replacement DX58SO Mobo after the original was shorted out by a headset (I know... stupid). The replacement I got back, works great (This computer I'm using to make this post). Since the board was replaced, I've swapped out the video card, power supply, all internal power cables, disabled Wake on Lan, disabled all power management options in Windows 7, and reseated all internal components...

But my computer consistently turns on, approximately 3 seconds after it is powered down. As you can see, I've replaced most of the components. Second, I've removed component one by one, testing it, to narrow down the component that might be causing it. But to no avail, with bare minimum... the unit still powers back on after shut down.

Can I have any more ideas?