Lauren and my iTunes became corrupt at the same time. When you opened iTunes, ALL the text looked like Hebrew with strange blocks in places. We installed The Iceman’s Apple Garamond fonts, but I don’t see how that broke anything.
After deleting all the caches, and trying EVERY sysadmin trick I know (ls -lart), I started disabling fonts via the Font Book.
It turns out that a (corrupt?) second copy of Lucida Grande got put in /Library/Fonts. By removing it, everything went back to normal.