Would that be DRAM bus voltage?
That's the one. I have the same board. If you have the latest BIOS from ASUS (I didn't check on the that came with mine), you'll have to set it to 1.64 or 1.66, because it goes in increments of .02 and won't accept the odd number, even if you enter it manually.
I'd try 1.64 first, then go to 1.66 only if necessary. According to the advice I was given by my RAM manufacturer (OCZ, I'm having issues with my RAM at the moment as well), a .01 increase over the max won't hurt the CPU or any other internal components, but it still scares me personally.
You also might follow the "Test Your System" steps from this thread.
to make sure your system is up to snuff and there are no errors. I had errors when testing with Prime95, which was my first indication that something was wrong.