Apple Pro tip of the week: validate your fonts
Fonts. You love them, I love them, we all love them. Occasionally this love can turn sour though, when a font goes rogue and becomes corrupt. Oh, the horror of a corrupted font.
Luckily, if you have Font Book (and you do if you're running a newish version of OS X) then the font corruption problem has a solution. Check out the tip at Apple's site for the full skinny (I don't want to ruin it for you).