Random crashes on STOCK clock

I have a Q9550, its got a 333 fsb by defualt
i will get random crashes every 3-4 hours if i keep it at standard clocking.
if i ramp it up to 400 then everything is peechy and i can keep it going for weeks on end.

i dont really mind running it overclocked but its just odd, and heat isnt a problem
default fsb idle is around 17*C, 400fsb yeilds around 27*C

yes

alright, since i had some free time yesterday i figured it would be a great time to try and replicate the error.
That was a mistake, i set FSB to default 333/667 RAM speed and stock timings.
After this, i would only get "overclock failed" and could not boot.
So i loaded the default BIOS, everything default and it just black screens or reboots 2-3 times.
If i change it back to 400/800 then its fine, but runs 10*C hotter because i haven't set up the fan speeds.

any ideas?