I have a very annoying problem.
When I maximize a window and than I change the focus to another window with alt+tab or by clicking it, when I go back to the first maximized window it stops to repaint. It means that window is still alive, i can understand it looking at the window title which is still changing but the only way i found to make the content window restart repainting itself is to detach it from maximize. At this point it works again.
I'm using ubuntu 11.04 with Unity with an ATI radeon HD4500 with propriertary drivers.