Ive been working on a similar prob for a few days.
First make sure you have the right ram DDRPC2700. Namebrand RAM, hate to say, its worth the extra. Power supply should be at least 350W of real (enermax quality) power. Flash the BIOS from ASUS, they just came out with 1016 I think for the A7V333. If you are running WinXP there is a patch for a poss OS error that can help this occur.
Check your jumpers. Sometimes the excellent BIOS setup can be double checked...
One more odd thing, look at this www.spectrum.ieee.org/WEB...ncap.html its not directly related to your issue but its damn odd.
Best,
Jim