Comment 33 for bug 269904

This sounds a lot like this problem, which is unfortunately a fundamental problem in the way the Damage extension is currently designed: http://lists.freedesktop.org/archives/xorg/2008-August/038022.html

The quick summary is that the X server sends damage events to compiz before sending the rendering commands to the hardware, and compiz can respond to those events before the damage has actually occurred. Some solutions have been proposed, but nothing has been implemented yet.