I recently upgraded my graphics card from a Nvidia Geforce 7300gt(256mb) to a Ati Radeon 5770(1gb). I have experienced to major graphical glitches. Both Occurred in instances and were spontaneous and were fixed by restarting the client.
1. In a Great Barrow Maze run random grey walls would appear in the hallways of the instance, I could walk through them but I couldn't see through them at all.
2. In a Dungeons of Gol Duldor run, a certain wall turned black and selectable objects(ie doors) became yellow when I looked at it.
I was told this was a driver issue, but seeing as macs dont really have drivers that change, I dont know how to solve the problem.
Note: Nothing of this sort occurred before I changed cards.