Cannot rename a Crucible user

[Phil Eccles]

Moving Crucible to a new server.

Moving authentication from Internal Directory to Delegated LDAP Authentication.

Want to change usernames in Internal Directory to match automatic usernames from LDAP. That way I assume all existing reviews will be kept with new username when user log on and new LDAP user added..

Anyway, every time I try to rename it says "this username is already in use".

Username does not exist in list of users or in dbo.cwd_user in database.