Screen goes black for a few secs randomly

Hi.

3 Days ago while I was playing Dota 2 my screen went black for one second and then it came back (the green led was on), later that night it happened again. The next day happened again when I was playing Star Conflict.

Today it did it like 10 times already, once while I was in firefox, rest in Star Conflict. At one particular map, where I had no problem playing yesterday. When I was facing a supernova (large burning fireball in space) the monitor went black then came back then black, when I turned the ship away the monitor was fine. I slowly moved the ship around to see when the screen goes black and when it reached the fire (or something beyond it).

Powered down pc, took it apart, cleaned it and checked if everything is connected nice and tight. It had some (a lot) of dust, carefully removed it, cleaned the cpu and the vga fans both. Started pc, started firefox, winamp and star conflict (these 3 program were running when I had the black screen), I got this black screen for a second in the garage of the game.

Right now im going to reinstall my graphics card driver, will update with result.

In the meanwhile. What can cause this? How to fix? I googled it before I came here, some people claimed its dead transistors on the motherboard, some said its memory fault, someone else said its the cables, some other dude said its vga and go replace it....none of these guys had a solution.

PC specs:

win 7 64 bit (2 months old install)
2*2 GB 1333mhz ram
Radeon HD 5670
Asrock m3n78d motherboard
AMD athlon II x2 250
Benq G2420HDB monitor

Update:

Reinstalled the vga driver, now whenever I start a game the screen goes black and comes back after a few seconds, then goes black again and again and again. I have music in the background. If I close the game with alt+f4 the screen fixes.

Games I tried: Dota2, Rift, World of Tanks, World of Warcraft, Kotor2, Star Conflict
I have other games too but didnt bother with them.

So, what now? If you tell me to buy a new vga I will stick a screwdriver in your arsehole. I have no money to buy a new one.

Boozad said:

As much as you don't want to hear it it sounds like your GPU isn't up to the job. Have you tried turning down the settings in-game?

I'm quite partial to screwdrivers up the arsehole so I'm not to worried about the repercussions of posting this.

Its quite hard to navigate in a game when the screen is black most of the time and comes back to normal every 2-3 seconds for 1 sec