I am having a similar problem to this. I just built my new comp (see sig) and had everything up and running for about a week (No OCing yet). Last night, I shut down the computer as usual, only to find that it wouldn't POST this morning when I turned it on. The screen is receiving a signal, but there's nothing but blackness.
After troubleshooting a bit, I found that resetting the CMOS allowed me to POST and get into the BIOS setup, but after changing the settings back to how I had them and hitting "save changes and exit" the system would immediately shut off, then restart ~2-3 seconds later and fail to POST again. This problem has never occurred before today. Nothing I know of has changed since yesterday when everything was working
Do I have a bad Mobo? I am still within Newegg's 30 day replacement period, so is that my best bet, or is there anything else I should try?
You know, I was freaking out about a similar problem early into overclocking my build. All I got was blackness. I checked ram, reset CMOS a million (ok, not quite a million) times, unplugged everything SATA, disconnected and reconnected CPU fan. All I got was blackness, and no beeps.
So, I decided to pull out the manual to figure out what was wrong. Since no PC speaker is installed on the mobo by default, I found one in a box of other computer stuff, and plugged it in. I decided to follow instructions for once in my life and use the manual to diagnose my problem. It gave me the beep signifying a video card error. I checked my video card and it looked ok, power was connected etc., but then upon closer examination I noticed it wasn't quite in all the way.
I gave it a nice little push, and poof. Problems disappeared. Still running strong to this day. Have you connected a PC speaker to "beep diagnose"? It might not help at all but it's an idea.