im guessing you use suitcase- i get this too. it seems to be when it tries to activate a font that you also have as a system font- ie helvetica, or lucia grande. its a pain- and the only way to fix it is t re-start the app (the one with the gibberish text, not suitcase). I'm toying with the idea of replacing all the system font with postscript versins- but im too scared right now, but i think it will fix it.