Apple's kbase document 106639 lists a easy sounding fix to the Classic startup halt that ends with the message "You are running Classic without superuser (root privileges). Ensure that TruBluEnvironment is setuid and owned by root, or reinstall your Mac OS X System Software."
Unfortunately it didn't work for me, and it took forever digging up a fix in an unrelated article. The problem wasn't ownership, it was the setuid bit. In the Terminal, type:
% cd /System/Library/CoreServices/ClassicThen go inside the ClassicStartup.app:
% cd "Classic Startup.app"/Contents/MacOSand type % sudo chmod ug+s *then type
% chown root *And your Classic should work again.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020428232843797