I have this Ubuntu-15 problem. I disabled global menu bar to switch to the window's title bar using ALL SETTINGS-APPEARANCE-BEHAVIOR. It switched OK, but now, for example, when I use NetBeans's window in maximized state its menu doesn't work. For example, I try to select the FILE menu, but no drop-down items appear - only some flickering. And the same is with a lot of other programs. When I had global menu bar everything worked fine!