I can't go past the ASUS Splash screen

I have a system I built over a year ago, that has been as stable as they come up until today when I tried to upgrade my RAM from 4GB to 8GB.
This is what it is:

ASUS P5N32-SLI Premium
Intel Core2 6600 2.5
CORSAIR XMS2 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800
ANTEC HE550 550 Watt Power Supply
BFG GeForce 8800 GTS 512
Windows Vista Ultimate 64-Bit

Like I said, I have never had a problem with this configuration and the 4GB of RAM, and today I added 2 more sticks of the exact same RAM, and started getting BSOD, hangs at login screen, hangs during boot, and plain ole crashes to a reboot.
I started taking out the new memory one at a time until It was fine again at the original 4GB. Then I put the new RAM in the old RAM's slots, same problem. I went back to the original configuration, and now I can't even get into the BIOS. I turn it on, the MoBo start up screen starts prompting me to press del to get into setup, or tab to see POST info. THE END. Nothing happens after that. No bootup. No buttons do anything. I have tried all the different RAM in combinations of slots, and nothing cures this problem.

What. The. Hell. Happened. And how do I fix it?

I have tried clearing the RTC and CMOS via jumpers and batteries, and all that jazz. This does nothing.

Yes. I quarantined the new RAM after nothing would start. I even have it down to one of the original 2GB sticks in.

This RAM is 1.8V.

I'll try doing it all again.

Another symptom was when I first put all the RAM in, the system wouldn't boot. When I took out one of the 2GB modules after my initial problem, everything ran fine until I tried running a 3D game, at which point the whole system locked up. That is when I took out the second new RAM module, (back to the original 4GB) and everything seemed ok. I then put a new one back in to make it 6GB, and it hasn't booted since.

Try to bump the Ram to 2.0 V and if u have options to bump NB and FSB voltage try to bump them to +.1V each.

More sticks often require slightly more voltage. Try bumping it up .01~.02 volts at a time until it gets stable. I would not exceed 2.0 volts though, if it all is rated at 1.8
Too much voltage will cause it to get hot, resulting in the same instability.