i failed to go above 450fsb for my x3350 on p5e3 premium with bios 0401. then i flashed to 0204 bios and i manage to hit till 473.

here is the setting i use:
vcore 1.36
cpu gtl 0.66 & 0.67
vtt 1.36
vdimm 1.8
vnb 1.41
nb gtl 0.67
sb auto

it might be not prime95 stable, but multiple PI 32m is no problem..

but then the 0204 bios is not good enuf, i failed to enter my vista few times. i thought my oc screwed up my os but then i realize it was bios issue.

i flashed back to 0401 and guess who's back again.... the 450 fsb wall

so it's not about the voltage settings, i'm pretty sure most of us here is experience enuff to test it step by step and to know whether it is insufficient voltage or other matters that cause the oc to fail...