Hello again!
Listen... looking at those pics again after all this time something struck me :bangin: ...
I am thinking along the lines of maybe a corruption in how the card/driver works out the z-buffer, either in the AF/Trilinear filtering stage or just a general issue with the Hyper-Z technology.
I would consider using another driver set...I have recently upgraded from the ATI Catalyst reference set to the latest Omega drivers based on the BETA Catalyst 4.12 driver. My games run a lot better and my image quality, especially in HL2 and 3DMark05, is an awful lot better now. You can download them from here:
http://www.3dchipset.com/drivers/ati/omega/index.php
Install them and let me know how you get on. Because if that doesn't work the next step will be trying to flash the BIOS, which is easy if you follow my instructions and play safe btw!
Have fun!