I'm not sure if this is merely an ATI thing but far as i can tell others are seeing this exact same thing.
Things i've noticed
Prims appear / disapear at random especially when in using the alt look mode with mouse and near an avatar with many prims. It seems that prims are being moved? or scattered at close range and the textures seem to disapear at random intervals.
I've added these two pictures so you can see a mere sample of whats going on.