If the user registration fails for some reason (in my case because I created a lang/sv.yml but not the other translation
files needed) the user is only partially created. (I also got an error message)
When retrying (having removed lang/sv.yml) the user registration failed because both the username and the email address
were already in use, but the user did not show up in the user table in the admin interface.
Creating a user should be done atomically inside a transaction in order to fix this.
I repaired my database by manually deleting all references to the user from the database.
I realize that I screwed it up myself, but having foreign key constraints and using transactions really improves the
reliability of data stored in a database.
This with redmine 0.5.0 with a postgresql backend.