Hi! 
I'm back. 
 
 
My current ATI card also has the same problem. 
OPK was right, it only occurs when I turn on adaptive AA. 
However now it can be enabled in the drivers without poking around in the registry. 
I use Catalyst 6.5 and an X800XL. 
P.S.
My old card was an ATI 9800Pro.