Increase DRAM volt to 2.20v. I've never seen any DDR2 800MHz stick running at 4-4-4-12 that would require less than 2.00v to stay stable.

That and I think you need to go with 1.51v on your Northbridge. Why? Because 4 sticks of RAM running at 4-4-4-12 is a lot for the Northbridge to take.