So, I just got a new graphics card (x1950pro), uninstalled the old video drivers the best I could, popped the graphics card in, started up fine, installed drivers, rebooted, black screen at the login. It still continues to run, you hear hard drive activity and people messaging on MSN, but no video. So, I tried a clean install, same deal. I then tried xp 64-bit, same deal. I've tried a few different versions of the driver, a third-party version (omega), just the bare inf's, all with the same result. If I boot with VGA mode, it runs 100% stable, no artifacts or anything, but if you try to change any setting in display settings, black screen. My friend has a similar system to mine (just different RAM and HDD, and he has the 4coredual rather than the 775dualvsta version of the board, though if it comes down to it he does have a spare of those..) and his never had any issue, and I tried different RAM with no luck.I'm doing windows updates now to see if there's any hotfix that will help.

Hardware:

E2140 @ stock rate for testing
Asrock 775DualVSTA
Sapphire PCI-e x1950pro 256mb (popped in an old 6600gt, worked flawlessly, so it's definitely specific to the card)
4GB pqi DDR2-1066 (also tried 2GB DDR-400)
Acer2017(also have a crt on vga just for testing)
Ultra 550w PSU (also tried a few other PSU's)
2x74GB WD Raptor (tried other drives as well)

EDIT: I also did flash the BIOS with no luck, and I might add that Sapphire tech support sent me the wrong BIOS and bricked my card, which I luckily was able to recover by booting with an old pic graphics card and reflashing the old BIOS.

i had this issue and i knocked a ram dim slightly loose

Check your cable to your monitor for type of cable, DVI-I, DVI-D ??
THEN make sure your monitor setup screen (access by physically pressing the buttons on your monitor menu adjustment and settings buttons) and make sure your monitor input setting is THE SAME. It may be incorrectly set to "Auto Search" by default, and not as DVI-D (or whatever your input cable type is). Worked for me! http://mysite.verizon.net/fibre/PC/PC.htm