Memory timing issue?

Gigabyte MA785GM-US2H
AMD Phenom II x2 550 BE
4GB Patriot Viper II DDR2 8500 1066
Vista 64 bit
XFX Radeon 4870
Antec BP550 PSU

I'm confused here and need advise. I built my system a couple days ago. Ram reported 800 instead of 1066 in bios. Changed voltage from 1.8 to 2.1 per ram specs and manually set clock to 1066. Great, everything working fine. Playing COD4 with no problems. Reboot to check timing and go into bios again and see timing at 5-7-7-16. Manually changed timing to 5-5-5-15 as noted on ram specs. Reboot and launch COD4. After 5 minutes of playing PC locks up and blue screens. After recovering I set timing back to auto (5-7-7-16) and launch game again. No problems. When I run CPU-Z the timing table for SPD shows 5-5-5-15 but the timings tab shows 5-7-7-16? Any advise would be appreciated.

Thanks in advance

Bump