WOW background gone...Follow

I tried at blizzard and they were confused, hopefully you guys can help me out.

Everytime I enter a major city, the city falls apart. In the UC in the main party it will be ok, unless I go to the canals then everything will disappear but the people and lamps the rest is a teal background. Some times I can see a jarble of colors and shapes and when I walk through it everythings good on the one side, but if I look back everythign trips out.

The same thing happened in ogrimmar, in the part where it says ogrimmar everything is good, but If I got to the valley of strength or anything, all different patterns and stuff show up. When I leave that part though everything is cool.

I have a nvidia geforce4 440 P4 1.7 and 384 ram, not the greatest I kno but it meets the minimum specs. I updated the drivers for the card and I have all the settings turned down.

Any ideas?