I have exactly the same problem, Using compiz fusion with Ubuntu gusty and the proprietary Nvidia driver (GeForce 8400M GS). I have noticed that the problem arise more frequently when I use two screen.
I have exactly the same problem,
Using compiz fusion with Ubuntu gusty and the proprietary Nvidia driver (GeForce 8400M GS).
I have noticed that the problem arise more frequently when I use two screen.