I've got the same problem. nvidia card + compiz + nvidia official driver + Unity beta2 (fresh installation - yesterday).
The white blank window (with only the title bar visible) is sometime for the window with focus, sometime for all windows open, and sometime time it seems random. The wall paper is completely white (in fact i think that it is nautilus-desktop (?) )
I've got the same problem. nvidia card + compiz + nvidia official driver + Unity beta2 (fresh installation - yesterday).
The white blank window (with only the title bar visible) is sometime for the window with focus, sometime for all windows open, and sometime time it seems random. The wall paper is completely white (in fact i think that it is nautilus-desktop (?) )