This happens for almost any drop-down menu, but is most jarring for right-clicking. Here is a screenshot of the problem: http://i.imgur.com/ZRrV4IP.png. As you can see, where the drop-down menu should be, there is a tiny squished copy of the entire window, including the ACTUAL drop-down menu somehow (so at least it's not infinitely recursive). Sometimes if I move the mouse as if I was selecting something from the menu, it will flicker back into its proper state, but sometimes not. Clicking on this "menu" still selects the correct option, but it's hard to keep track of where things are when it keeps flickering back to this. This didn't happen to me until after the Firefox 29 update installed. Things that don't fix this problem: - Resetting Firefox - Starting Firefox in Safe Mode - Installing the Classic Theme add-on I'm not sure how this even happened, to be honest. I'll work around it as best I'm able for now, but drop-down menus are really convenient and I'd like mine back.