some time ago, I made mention on here about the windows decoration being a but buggy in Compiz. Specifically, with regards to the close/minimize/maximize buttons disappearing. And most commonly with Firefox windows. This problem is more of an irritant than a show stopper and can be resolved, at least in my case, by minimizing and then maximising the window by pressing on the panel button for the window.
However, this evening, I have noticed a specific set of actions that will guarantee to cause the buttons to disappear:
If a Firefox window is open but minimised to the panel. If I then open a new Firefox location by double clicking a launch icon (on, say, the desktop), this will force the existing open (but minimized) Firefox window to unminimize with a second tab that is displaying the launcher link I just doubled clicked. However, at this point, the windows buttons have disappeared. Again, this is fixed by clicking the panel button for the window to minimize it and then again to maximize it,. At which point, the buttons are there again.
I just thought I would mention this as this is the first time I have actually been able to predict when the buttons disappear. Hopefully, it might give some clues (to people more knowledgeable than me) as to the underlying mechanisms behind ths bug.