Graphic card error while playing games. Pls help!

I have some major problems with my 64bit Win 7 system and my gfx card and I would like to send 20 bucks via Paypal to whoever who can help me resolve this as a little thank you.

Whenever I play a game (any game) the video card driver will crash (pretty much after 1 to 3 minutes playing). I get some weird squares on the screen and sometimes a bsod or it will recover and the screen has some weird lines all over it that might go away after the next reboot (or it takes several reboots to get back to normal).

Running just windows and regular applications like firefox and so on is no problem at all.

This seems to be a hardware problem because it persisted even after formatting and reinstalling everything (including a new Win7 ultimate install, I had the same problem with Vista 64bit before) and trying just the windows drivers, just the ati driver and finally the ati driver along with catalyst. My PSU should be fine (Thermaltake 650W) and I dont have overheating issues.

I have a Radeon HD 4850 and my computer is a QuadCore Intel Core i7 920, 2800 MHz (21 x 133).
A complete Everest report with all details about my computer and gfx card can be found here:
http://waszum.com/misc/Report.htm
http://waszum.com/misc/DxDiag.txt

I found sites about the atikdmag error and tried removing some ram but it didnt help. The atikdmag error just showed up sometimes. I also used the iso from memtest.org and ran the default tests and my ram seems to be fine. Is it maybe the ram Timing? Im absolutely clueless and as I live in Thailand at the moment my options to get to a computer specialist are rather limited because whenever I did this they recommend me to buy new parts... even though this never really solved the problem.

Any help is really appreciated!

I say it is a GPU or video card memory issue. What are the idle temps of the video card, and what are the load temps during a game?

Usually heat is the issue, or if your video memory is going bad. I would call the manufacture and get an RMA for the card.