Update--
As of this morning, the game is completely unplayable -- it has about ten seconds before it balckscreens and I have to restart my computer the hard way. Four times this morning! It was going fine this past week, and suddenly today, it's rediculously terrible. Also -- this past week it was randomly logging me out of zones and kicking me to the character select screen.
So... I went to ATI, installed their super control CCC package, and followed the above instructions with the "Support DXT texture formats" and rebooted my computer. No change what so ever.
Is there anything else I should try? This is really frustrating, and it's an issue that needs to be fixed. I appreciate all the suggestions that have been given so far, but I would really like to get this game working. After three years of playing, this is a pretty nasty way to go, and I'm heartbroken at the thought of having to quit the game completely due to a technical issue.
Thanks.