[BSOD] Bad Pool Caller When Playing Games?

i started having this issue awhile ago, but never had much time to try to troubleshoot it, in fact, it went away for a little while...i will play a game (starcraft 2) for maybe 40 minutes or so when the screen will screw up, make a buzzing noise, go the bsod and try to restart the computer. sometimes it will restart without trouble.there's also times where i will exit the game and go to Internet and it will crash then as well. at the blue screen, i have seen these two error messages the most:bad pool caller irql not less or equalreading through others' posts on various sites, i have done the following:updated various drivers, including my videoupdated biosinstalled the new version of nortonran memtest (no errors)it also seemed to me that the machine was running loud, so i opened it up and blew out the dust. after this, the problem stopped for about a month. now its back.i'm going to run memtest a few more times, swapping out the ram, because it sounds like it doesn't always catch stuff the first time.