CPU will not turn on, thought it was PSU, but it's not!

My situation is as follows:

[ul]
[li]I bought a new case and moved my stuff over.
[/li][li]Everything worked fine for about 1 week
[/li][li]I noticed that when i put my desktop to sleep at night, it would start to wake itself up at some point and just spin (no visual output, etc)
[/li][li]I forced shutdown, and it would not start up again
[/li][li]The green light on the motherboard goes on indicating the mobo has power (right?), but nothing happens when I hit the power button
[/li][li]I replaced the PSU and tested, nada.
[/li][li]I replaced the case, using the power button from my old (and still working) case, nada.
[/li][li]I did all my testing with minimal components. No graphics card, no HDDs, no fans (except for the processor heatsink fan).
[/li][/ul]

Basically, I’m out of ideas. Can anyone provide any insight into what might be the problem? It annoys me that the motherboard power light goes on but nothing else will…

ASUS P5Q SE
E7200
4 x 1GB
EVGA NVIDIA 9600GSO
Thermaltake 500W (replaced with Corsair 400W)

Any help will be GREATLY appreciated.

-Sam

Just an idea maybe a power surge at some point took out your bios..