Are you getting ANY beep codes at all? A key to their meanings is on the right side of the page
HERE , just select your Bios type (Award, Phoenix, etc).
Have you re-seated the RAM and Video Card several times? I mean, it seems like they are totally seated sometimes when they really aren't. I've had to try several times on both of these items.
Also, have you tried getting it to boot OUTSIDE the case? It may be grounding out at some spot underneath the board against the case. It can act just like what you described when the mainboard is shorting against the case.
The only other thing I think of is a faulty power supply, but you didn't mention the cpu fan not spinning, and I assume the power supply fan is spinning, too.
Good Luck.
Post your progress.
See ya.