I had the looping Finder problem. It's something in the Startup Items which is not compatible with Panther (I had about 8 or 9 startup items).
Reboot holding down Shift. You should see "Safe Mode" before you get to the login screen. After you login, the Finder should be OK. Go immediately to System Preferences, Accounts, Startup Items. Remove all of them from the list (remove using the "-" button, don't just check or uncheck the Hide box)
This fixed it for me.
