Help with freezing on new overclock, no blue screen though

hi all
following the overclocking guide for i7, i have reached a clock of 3.8ghz, which is all i plan to go to.

no more blue screens, at least i dont think so.

problem i have though is that, say, im playing a game, sometimes, say in cod 4, if im hit by a random sniper, the computer compleatly frezes as if it shat a brick over the sudden change from 1st to 3rd person. not just sniper though (that was an example) it can happen at any time when something similar happens above.

when the comp freezes, there is no blue screen. image last seen is left on the screen. nothing is responsive, including keyboard (pushing the caps lock button, no light goes on / off)

am forced to have to reset the computer.

did originally notice this on vista but am using windows 7 now.

it could be a graphics card problem as well as this is the only thing i can blame

I run a HD 4870 x2, which by the way sucks balls.

sorry if this is in the wrong section, its just i only notice this happen when overclocking.
any ideas on what could cause this to happen??

thought u were a moderator!
probs soon ha ha

anyway err i think it happened once. yeah happened on vista with sound most of the time, rest of the time on 7 its been silent, which im happy bout ha ha, try playing in silent then all of a sudden BLAAAAAAAAAAAAAAAAAAHHH!!! very anoying

i have added some voltage. surprised though when ocing, was still at 1.256 vcore at 3.8 ghz. put it up to 1.300 i think from memory. stable enough on prime 95

Nice, hope that works, make sure you prime test it for 12hrs.

thought i saw a moderator under your pic at one stage. oh well, lol