Some 965 chipsets motherboards have FSB speed bumps, or clock regions which are unstable, for example 390 through 430. Sometimes all it takes is driver updates, but more typically, it requires leapfroging over the uncooperative clock regions. However, as RobsX2
pointed out, don't forget to tweak Vdimm and / or timings for stability at DDR2-900.
Now I can aim for 3.7
Typically, above 1.35 Vcore, each .05 increase = ~ 100 Mhz increase, and ~ 3c temp increase. 8)