I don't know how to reproduce it. It happened with a fresh boot. I opened Google Chrome (which was not maximized yet), maximized it, then noticed I couldn't access the Unity menu. The Super key worked fine. I then un-maximized the window, saw the launcher appear, re-maximized it, and the problem recurred. Several minutes later it was working normally again.
I don't know how to reproduce it. It happened with a fresh boot. I opened Google Chrome (which was not maximized yet), maximized it, then noticed I couldn't access the Unity menu. The Super key worked fine. I then un-maximized the window, saw the launcher appear, re-maximized it, and the problem recurred. Several minutes later it was working normally again.