I seem to have a problem with directx games on my X1900XT 
If I start Counterstrike Source or Test Drive Unlimited I get a constant stutter. On CSS If I ALT+TAB once it doesn't go out of the game and the stutter goes
I was using the Catalyst 7.2 drivers and had the problem. So I upgraded to the catalyst 7.11 drivers, but it is still exactly the same
(also lost 40+fps on stress test?)
The stutter seems to be every second or 2, but it is constant and is really annoying to have to ALT+TAB out just to fix it.
Also on OpenGL games like Quake3 it is ok, no stuttering or anything.

If I start Counterstrike Source or Test Drive Unlimited I get a constant stutter. On CSS If I ALT+TAB once it doesn't go out of the game and the stutter goes

I was using the Catalyst 7.2 drivers and had the problem. So I upgraded to the catalyst 7.11 drivers, but it is still exactly the same

The stutter seems to be every second or 2, but it is constant and is really annoying to have to ALT+TAB out just to fix it.
Also on OpenGL games like Quake3 it is ok, no stuttering or anything.