Originally Posted by The Sandman
Have you removed/installed or changed anything?
Which CPU and bios are you running?
I've heard of things like this turning out to be either bad CPU socket contact which was simply remedied by R+R and inspect for anything odd or as odd as it may sound, I believe a few had found a bent pin by surprise as they were always careful when installing. You probably already know this, just something to watch for.
I'm using the latest non-beta bios and I haven't messed with the cpu socket area in two years. One month ago I upgraded the ram to Corsair 2x4gb Vengence ram 7-8-7-20 timings. Didn't notice any problems. Then I installed a SSD 6gb/sec drive only to remove it as my current ssd raid array benched slighly faster. Then I changed the monitor hookup from hdmi to dvi and this is when I noticed this issue.
I swapped the old hdmi monitor back and am using it now and it booted up from cold no problems this morning. But this has always been a possessed system with problems as far as I can remember. Never could handle triple 6970 crossfire without freezing and locking up. So I put those video cards into an X58 rig where they're happy and stable. Have a single 9800GT in there now and if I put a second nvidia gpu type card in the second or third pci-e slot it just wont post. So not sure if this a video card issue.
Funny thing is that I spoke with Asus tech support about the two video card issue and they said its an AMD chipset board and prefers AMD cards. I was trying to get multi monitors going with the second gpu nevermind sli which I know just doesn't work not with out mods. But this board has been one of the finickiest boards I've ever used since my old 680i board from years ago!