After doing a Carbon Copy Clone to my second internal drive, I installed Panther. Went back and Carbon Copy cloned my apps/preferences/etc back to my main hard drive.
All my OS X apps work except for Panther's own: like Mail, Installer (which hangs but does nothing) - yet iTunes, Safari do work.
Mail launches and instantly shuts down.
Installer hangs.
I deleted APE Manager, FruitMenu and Default Folder and restarted and repaired permissions and restarted.
And the problems continue.
Your help will be greatly appreciated.