Assuming your system is stable when not overclocked, and that you are running at 1:1 with the fsb (754/2 *9 = 3.4 Ghz) start by easing up on your memory timings and see if that helps. You could also try running your cpu at an 8 multi with 425FSB and 850Mhz memory with looser timings, if your motherboard allows it and try to pass a 12hour prime95 blend run. If that doesn't help try slowly reducing your overclock until you start to feel better stability. If none of that works then it's more likely to be a difefrent component such as the psu.
OK so just as i saw, there are two 12v rails, combined they should give the 460 gtx enough juice, so the PSU might not be the problem here, but i am still suspicios, I do not want to give you bad advice, maybe solve the memory/OC issues and go for the new PSU solution as last resort if nothing helped. For PSU, if you want a cricket in your PC (risk of coil whine), get any Corsair PSU, altought they are one of the best PSUs out there, that is my only experience with PSU, i think Enermax make good PSU also. One last thing, your specs say modded bios, maybe try using default BIOS and set everything at stock, wait a few weeks and if no freezes arise then it is a bad OC and the PSU is fine.
Guess the problem went away somehow.. At least for now.. ~2 days with stress testing / gaming / watching hd movies and no crash or instability yet.. Hope it stays this way.. Looks like the pc had just a slight cold which got cured
Ok it didn't go away.. Reinstalled windows to rule atleast this out, and it's still randomly freezing. Removed the overclock now, as suggested, will report back after a few days..