Does it ask you for a user ID and password when you first get into AppAdmin or does it give you the Unauthorized message immediately?
If it asks you for the login, are you using the default UserID and Password?
UserID: Administrator (the uppercase "A" is *very* important)
Password: ciscocisco
Once you enter these, you will be able to go through the initial configuration and re-choose the accounts that you want to access the AppAdmin page in the future.