I've noticed that if you uninstall ATI drivers without using something like drivercleaner, they are still in your C:\Windows\System32 folder and Windows will pick them back up when you reboot.
At one point I had to boot into safe mode, go out to that folder and delete anything that began with "ATI". Catalyst drivers are now at
5.10, I've installed them on my machine and they work fine with FFXI.