This is another of my favorite kind of posts, the "I saw something wrong but I don't know if I'm the only person affected by this".
When it happens : not in the Visual Editor, in HTML editing mode.
The solution is simple : hit Space, and the menu pops up, af if I had clicked it.
But other users may be taken aback or miss the trick to hit Space.
I don't know if I'm the only person having this problem, but at least, I've come to report it :)