I am using Ubuntu 11.10. Sometimes the window controls don't work. If I click on any of the icons on top-right or top-left they just become colorless and fade away, as though that are not present.

The window has not frozen, as I can click inside the window and continue to work with it. The moment I click inside the window the titlebar controls regain their color, but when I click them again, they fade and bcm colorless.

As a result, I cannot close, minimize or maximize.

This is not a continuous problem, but happens very frequently.