Sean,
Feel free to send the admin credentials, and we'll take a look. However, the following are things we'll be checking, if you want to look first:
1) In the Install/Uninstall area, can you see the JFBConnect Authentication plugin? If not, it wasn't installed properly (we already know this, but good to check what Joomla 'thinks').
2) If not, check the /plugins/authentication directory for jfbconnectauth.php and .xml files. If there, delete them. If they were copied there manually (or FTPd), that will prevent the Joomla installer for properly installing (overwriting) the files that are there.
3) Check the permissions of the /plugins and the /plugins/authentication directories.
4) Try to re-install using the Joomla installer and see what happens.
Hope that helps narrow things down, but again, we'll do what we can if necessary. Through the Joomla admin though, it's not always possible to remove or re-permission files as necessary, just so you know.
Thanks,
Alex