Screen Goes Black For A Second Every Minute Or So During Gaming

This is the weirdest problem that iv been trying to solve myself for months now. Basically while playing pc games the screen goes black for a second then comes back and resumes as normal. thing is it is totally intermittent and slightly different for different games. e.g Titan quest, mass effect 1 and 2, need for speed shift 2 unleashed, HoN - it will go black for a second or so but the game will carry on as normal, sound continues and when the short black out is over my character has carried on moving as normal just without me being able to see what is going on F1 2010, Grid, Quake live - No black outs occur whatsoever Dead space, Dead island - the blackouts seam to affect the game either pausing or freezing the game when they occur to be honest it looks to me like the graphics driver is stalling for a few seconds and then recovering, But iv updated my graphics card drivers 4 times since this problem started and that hasn't changed anything, i even completely uninstalled the graphics drivers and reinstalled them to no avail. The only thing i haven't done is reinstalled windows and replaced my graphics card. Both of which i don't want to do unnecessarily. I read somewhere that video codex could be the issue, so a while ago i uninstalled k-lite and it seamed to fix the problem in mass effect 2, (not completely but id did seam to reduce it (coincidence?)) but after i finished that game i noticed it cropping up in other games again.So basically the advice im asking for is, Do you think its a hardware problem, should i invest in a new graphics card? or do you think its software that either a fresh copy of windows or some installing/uninstalling combination of different software might resolve the issue?