Recently we updated our prototype site that had registered users. However during the registration process we re-initialized our database and therefore removed the user's registration.

When the user went to login to our application he tried using his registered OpenID, but since the database was re-initialized we didn't have his OpenID information. Instead of telling the user that we didn't know who he/she was and giving them the option of registering a new account or trying to figure out who they were by contacting us or forgotten password, we displayed an Internal Server Exception. Not very helpful to the end user.