MACUPDATE ADMIN  Have you tried using a system utility such as AppleJack or Onyx to do a 'deep clean' of your system caches? It might help.  
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G4JAY  Yes, I use MainMenu to batch process all my system cleaning tasks quite regularly. Once I get Leopard, I'm going to do a system enema and hope that clears this glitch.  
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UMAROMC  Have you attempted Recalibrating to create a new color profile? Maybe messing with those gamma, hue and saturation settings a tiny bit could be it... :P

Another idea is to try aticcelerator to lower the clock speeds of the VRAM and GPU, I think it works with the X1900 XT—dblchk.  
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POWERTOWERPRO  The artifact issue with the GPU is a known rev1 problem and if you mac is still under its one year warranty a quick call to apple care will get you a brand new rev 2 card. I did this 2 months ago. There is a HUGE forum on blizzard on this. Tons of people have got new cards. Here is the link (you can thank me later):

http://forums.worldofwarcraft.com/thread.html?topicId=94000596&sid=1

My post with direction on how to handle the apple care reps:

http://forums.worldofwarcraft.com/thread.html?topicId=94000596&sid=1&pageNo=10

Read the post from "Elderclass" Thats me.  
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G4JAY  Are you SURE this is the same issue? Most artifacts can be seen in a screen shot. When I do a screen shot, they go away. Did you read the URL in my first post? My warrenty expires on this thing in like 10 days!!!  
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G4JAY  See... this is what I am dealing with:

http://www.dganimation.com/CIMG3574.jpg  
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