Well, the cause is pretty apparent: it's using the large system font size (13pt) for everything, even the text that should be drawn using the small system font size (11pt). It could be a corrupt font, I suppose, at which point you might want to consider using Pacifist to re-extract Lucida Grande.dfont... it could also be the case that you have another copy of the Lucida Grande font somewhere that's overriding the built-in system version. Lastly, if you have TinkerTool or Silk on your system, make sure they're not overriding the system fonts.
Good luck!