Screen flashes to dark purple while hunting inside unrest...?

[Ayrebourne]

Hey all, so my graphics repeatedly go all screwy whenever I start to hunt within the castle inside unrest. They're fine when I stay outside, but as soon I go inside and look roughly northwest, the screen will flash to dark purple and stay that way until I move my character a little and it goes back to normal. The only fix for this is completely logging out of EQ and entering again, but before long the flashing is back. I'm running a GeForce 9800 GT, and wondering if anyone has any suggestions. I've talked to people in game and they've had similar problems.

As a ranger who attempts to pull, it makes it very difficult when I cant see the hallway I'm running down. Any suggestions, let me know! Thanks guys.