All I'm proposing is that BEFORE you conclude that a vendors drivers are shatty you better be damn sure it's not a conflict within your system-and this requires (if all else fails) a fresh OS install regardless of the vendor-(I've done it for nvidia).
As I suggested earlier
Completely unsinstall the game-manually remove the system folder and then delete the registry keys-then reinstall the new drivers by removing them through the control panel (along with the ati control panel), reboot, delete the ati folder in the primary harddrive, remove all the ati.dll files in the system 32 folder, then use regcleaner to delete all the ati registry keys, reboot, defrag, and install new driver, reboot, then install control panel, reboot and you should be fine.
I did this with my nvidia cards too changing between dets and i still had problems.
rogo