Ahhh i see.
No duel bios. Well i dont blame you then. Now as for the rounding error. I found that if i loosend the timeings on my ram up one notch, like, 2.5-7-4-4-7 My pcmark score went way up, and the rounding error went away. Try loosening you timeings up a tad. maybe the ram doesnt like that clock with the tighter timeings. I found that when the Ram was set to SPD, i got a ton of errors anywhere from 2.850- 3.0 and at 333mhz with the ram. So when i loosened the timeings i got A major stability boost and a great pcmark score. 1000 points higher. 3dmark also went alot higher. And Prime ran for 24hrs without a problem.
Before i loosened them I got rounding errors after third prime teas. I think its #3 4000 whatever it is there.
Also try a voltage bump on the ram. That might help also.
good luck, and check back if you can.
Harry