current rig:
I7 2600K @ 4.5Ghz - 100x45 1.19vcore
ASUS P8P67 DELUXE
Mushkin Radioactive 16GB (4 x 4GB)
SLI 2x EVGA Superclocked GeForce GTX 580 (Fermi) @900/2100
CORSAIR CMPSU-750TX 750W

I recently upgraded my case from a smaller lian li to a much larger coolermaster case. I did this for two reasons, the case was old and beat to , and I needed to make room for my arctic Accelero Xtreme II's for my 580 GTX's.

There were NO other changes, just the case swap and VGA cooler swaps.

I was running both of these cards in the old case (albeit a tight fit), and everything worked perfectly, however, upon swapping everything to the new case, I'm getting a weird post issue.

Once I got everything plugged in, I had no post, no beeps, nothing. So I rechecked all cables, reseated everything, and started from a minimum, to include 1 stick on various dimms, nothing worked, straight black screens instead of posting. So I cleared CMOS, and voila, I get a post. It forces me to go into bios to "recover bios settings"

HOWEVER: If I go into bios, and make changes, it goes back to no post. if I revert to "optimized defaults", no post. If I do anything when I exit bios, no post. And the only way I can get this to reset, is to again clear CMOS (battery + unplugged only)

Now, if I go into bios, and just discard changes and exit, it posts normally and goes right to windows. (I'm posting on this machine currently)

So this means I can run the comp just fine once it's in OS, but if I want to make changes to the bios, or reboot for example, I have to clear CMOS. Even rebooting out of windows causes a failure to post. No beeps, nothing, until I clear CMOS again.

So my question is, what the hell is causing it? I was using an old bios, but I flashed up to 3602, this didn't fix the issue.

I'm at a loss.