Graphic Card Problem (ATI X600 Direct3D)

[ZyMar]

Hello!
First of all,
I'm running Windows XP V.5.1.2600 (SP2)
mainboard ASUS P5GD1 PRO
graphic card ASUS EAX 600 XT/TD (PCI-Express)
1 GB RAM
Intel Pentium 4 3.0 GHz (775 socket)
and I have Kaspersky Internet Security 6 active.

The problem:
A couple of weeks ago, there was no problem at all! Then, while playing Sacred Underground, sometimes the display froze for a second, and I got a message from VPUrecover that the graphic card "Had stopped responding and was reset succesfully" and I resumed my game. Those crashes were becoming more and more often, but I thought it was something wrong with the game.
3 days ago, I launched Google earth, and there was a mojor problem with the display. It crashed 2 minutes later.
I tried Morrowind too. I hasn't crashed so far, but still the textures are flickering continuously (and some are totally missing).
I think there is something wrong with Direct3D. (Even the little racing car in the catalyst cotrol center crashes after a while).

Done so far:
Updated my windows
updated direct X (which passes all the tests)
updated the mainboard's BIOS
installed the latest ATI drivers
I even tried the drivers from ASUS (2006/08).

When I'm not using Direct3d there's absolutely nothing wrong. Everything works perfectly.
Can someone help???

[ZyMar]

I finally lowered the mem clock a notch and everything works perfectly.
Thanx for the help guys, you've been really helpful...