Originally Posted by grey_1
maybe it does have to do with the video ram.
I don't know the technical reason for the bug, but I have the same card as you and the bug was reliably reproducible for me with driver 9746. One window would open black or the tooltips would go black, and from then every opened or redrawed window was black. This could be temporarily "fixed" by switching to a console and then back to X, but sometimes this crashed the X server completely so I had to reboot my machine.
The new driver, however, didn't show any black windows so far, that's why I was asking if anyone has already seen the bug with the new driver. If yes, I would disable the composite extension again because I have to work with the computer as well.