Reset CMOS, look in manual (done by moving jumper to 2&3 on my Abit AW9D-MAX). Then let the BIOS figure out what settings it'll set on the ram, and if its at 667, then select DDR2-800 in the BIOS, but don't mess with timings. My board slowed my DDR2-800 G.skills down to 667, but there was an option to select DDR2-800, which I selected, and its back at 800... I tried messing with the timings but ran into same situation as you did. So I cleared CMOS, and put it back at 800, but left the timing alone.
C2D E6600 @ 3.15ghz w/ 1.35 vcore
2GB G.Skill DDR2-800 (4-4-4-12)
XFX 7600GT xXx