This bug is similar to the VBO rendering bug on ATI systems. Going to an "extreme high altitude place" on ati x1950 pro 512mb agp will cause the "invisible polygon/geometry dome" the windlight shaders/textures are placed on to become corrupt and every other section will render in "Black bands". this black band bug will also reflect in the water shaders when the sky should be as if they are an in world object. Once it starts it will stay in any sim, any server change, or any area you go until the viewer is restarted, changing any video setting will not reset it. Turning VBO off or on does not help starting with VBO off makes it happen, so it does not seem to have anything to do with the VBO bug other than looking like it.