The same happens when you have maximized window (eg. Firefox) and unmaximized on top of it (like Terminal). Unity shows only terminal menu, but you can't close Firefox without unfocusing the terminal (window buttons don't appear on top-left side of the screen when you drag your mouse over it).
The same happens when you have maximized window (eg. Firefox) and unmaximized on top of it (like Terminal). Unity shows only terminal menu, but you can't close Firefox without unfocusing the terminal (window buttons don't appear on top-left side of the screen when you drag your mouse over it).