I have some problems with some games. It's one of those black screen -> ''Display driver atikmdag stopped responding and has successfully recovered'' (-> Game crash) Errors

Some games work fine, but some start messing too often so it has become unplayable. What can i do to fix this problem or at least find out what's wrong?
I heard it's a Vista problem. is it?
PC Specs:
Intel Core 2 Duo E4500 @ 2.20GHz
3GB RAM (1x 2GB, 1x 1GB)
Club3d HD4850 512mb Overclocked Edition (Latest drivers)
580W PSU
Asus P5LD2-X/1333 Motherboard
Windows Vista Home Basic 32-bit
Let me know if you need more information.
List of games, in which i have gotten this error:
Dark Sector (Very often, Crashes the game, Sometimes even BSOD!)
Riddick: Assault On Dark Athena (Very often, Crashes the game)
Call Of Duty 4 (rarely and successfully recovers and i can continue playing)
Terminator: Salvation (Often, Crashes the game)
Warhammer Online: Age Of Reckoning (Very Often, Crashes the game, Sometimes even BSOD!)
And there's probably many more games....
