On my machine, Word, Powerpoint and Excel in Office v.X kept crashing/quitting on launch and even after deleting plists, prefs and identities, they still kept bugging out (strangely, Entourage was fine).
It turned out to be a corrupt font in the OS9 system folder. You can test this by quitting Classic, putting the OS9 font folder in the wastebasket and logging out. When you log back in again, you should be able to launch Word. Now all you have to do is find which font is corrupt before you put the fonts back.
[Editor's note: I believe there are some OS 9 utilities that help find corrupt fonts, but I can't recall any names at the moment ... anyone know of any?]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020110114013827