Comment 1 for bug 678028

The problem is more generic. Sometimes you click the close button (upper left 'x') and, if any, the underlying window gets closed insted of the foreground one. It is unpredictable wheter it is going to happen or not, but it can be very dangerous (for example google chrome doesn't ask for confirm and just closes up).
 I experience this bug with ubuntu 10.04, compiz disabled and nvidia driver.