try raising the ram voltage to 2.2V
you can probably run the ram at 533 then. which at 3.4ghz (i think that is 357? external clock/fsb speed. which is a very impressive overclock to say the least), which would give your ram (i think cpu/7...3400/7 = 485)a speed of 485mhz (970mhz effective). those ram, are they HZ's? should run that fast with 2.2V
i find my best performance/stability is to run my cpu at like 2.9 and ram set to ddr2 400, at which speed i can set the timings to 3-3-3-9-1T. its under 400 mhz, but plenty fast. with our amd cpus, the ram latency is more important than raw speed....unless you can get them to clock close to 550mhz (1100mhz) , at which point the speed increase eclipses the loose (5-5-5-15 2T) timings you have to set them at to run them that high.
if you can get the cpu to run at 3.4ghz with stock voltage...even if it takes like 1.45V and temps are okay...BY ALL MEANS run it at that speed and adjust your ram to be stable. most likely you will have to leave it set to 4-4-4-12-2T. or you can try raising the timings to 6-5-5-15-2T and see how far you can push them. if they are HZ, possible to get over 1100mhz.
your 3d06 @ 3.4 is pretty good. what gpu do you use? that benchmark is MUCH more gpu dependent than cpu. i get around 8500 with my sli 7900gs, everything overclocked a bit.
likely it is shutting down randomly because you are overclocked too high. or you dont have enough cpu voltage. or your ram is unstable. or or or lol.
your psu could be the culprit. but, if you are not raising the voltage on too many things at once, it should be okay. what kind is it?
i have a coolmax 550 sli and it works plenty good.