Checked around some, and it looks like one user had the same error (ttmkfdir segfaults on hoary) but not the same problems afterwards. No clue how a program that only reads from dirs could destroy fonts. You might want to check (and reinstall) if your freetype (2?) dirs aren't messed up, since it's what ttmkfdir relies on to work on the ttf files.

Edit: Oh yeah, forgot to sugegst what clout says. Try that first.