Why won't the quick reference buttons in the Inspector panel work?

I'm going through some of the Unity tutorials and have found that when I try to use the quick reference buttons in the Inspector panel (they look like little books with question marks on them), they don't respond. If I hover the mouse over I get a tooltip, but clicking on them does nothing. I'm in OS X -- possible bug for this platform? Or is there some setting I need to change to enable these buttons?