I got similar problem. The system was working fine, for about 1 week.
During bootup the mobs logo shows up, where I have a chance to enter BIOS, then the black screen shows up where it goes through a quick system check (I have quick boot enabled), then the windows logo shows up.
After 1 week, right off the bat, when I started it up the Mobo's logo shows up garbbled and after that the system won't boot up. It hangs at the black screen screen for a while..then windows gives me the options of booting up in normal mode, safe mode, etc (it all looks garbled though..but I can make out some of the text). But when I select normal or safe mode it still won't boot up.
I updated the mobo's BIOS to the latest one out there...didn't fix the problem.
If I unplug the monitors cable from the CPU and turn everything off and turn it back it..it works. Then when it feels like it wants..againt the problem shows up.
Videocard drivers are installed.
SYSTEM:
AMD 64 3200+ Socket 939
2 - 1GB Corsair Rams
GeForce 6800 GS video card
ASUS A8N5X mobo
all the info I can give.