I'm not sure what I did, but my scroll bars look like hell. In this picture, you can see them adjacent to the suggested questions and at the windows edge. What is that about?
This behavior is consistent across all applications -- at the top and bottom of any scroll bar, I see a tall grey box. And in some cases I get this wacky multiple horizontal scroll:
In trying to fix this, I managed to totally trash my compiz settings (What do I do about my busted GUI?) so now I've restored Compiz to its default settings and the scrollbars are still totally crazy looking.