OK so just about an hour ago I booted up my machine (which has been stable as heck and running beautifully for a little over a year- thanks EVGA!) I had my firefox browser open and went to plug in my digital camera to the front USB port- all of a sudden I got a message saying that all of my USB devices could not be detected- suddenly no mouse, keyboard or anything! I unplugged all of the devices and plugged in an older-style non-usb keyboard to try and shut down the machine- that didn't work either.
 
Thankfully I have a few spare PC's so i can post this request for help! My PC gets stuck at the bios screen now stating "keyboard error- no keyboard detected" and will not proceed into windows. It also shows only my DVDRW drive is being detected. I'm not sure what could have caused this, but it seems like a MOBO issue. Any advice would be welcome. Specs as follows:
 
EVGA E770 X58 Mother Board
2 EVGA GTX 570 1280 mb cards
12GB G.Skill DDR3 1600 Ram (3x4)
Quadcore i7-950 Bloomfiled 3.06ghz processor
WD Caviar Black 500gb Hard Drive
ASUS DVDRW Burner
Created Audigy SE 7.1 Sound Card
Atec 1200 Black Steel ATX Full Tower
Antec Twelve Hundred case
 
 
 

I don't want to sound like a broken record but.... it could be your PSU  which I don't see listed in your post.  I have come to find out (the hard way) that a bad PSU can cause all sorts of strange issues that seem to have nothing to do with a PSU.  See my attached post to see what I experienced.  Please read the whole thing and you will see what I mean.
http://www.evga.com/forums/tm.aspx?m=1431218 
Good luck.
ps. Did you try rebooting?

Thanks for the response- Yeah i did forget to mention the PSU- it's actually the same as yours- Corsair AX1200. It's been rock-steady since i put it together December of 2010- so it's only a bit more than a year old. This just happened all of a sudden and no matter what I try I can't get back into windows.
 
Yeah I've attempted to reboot many time with the mouse/keyboard in different ports without success.

Reset the BIOS and try a different power supply if possible in the system with it bare bones and see if there is any change.
 
Post back the results.

 It turns out it was the power supply. I installed an older Ultra1000 modular PSU that I had and my PC is running fine with it- booted up the first time. I guess I'll have to contact corsair and see about getting a replacement as it's only like 14 months old.

Glad you were able to figure it out.  Like I said, a bad PSU can cause all sorts of unlikely issues.  I found that out the hard way.