Backed up and restored a database the other day, but of course the network users arent setup properly cause there actually stored in the master database..

So i recreate the user on the instance which is fine , and then try and regrant it permissions on the database but it fails because its already there…

To fix…

User DATABASE
EXEC sp_change_users_login 'update_one', 'usernamehere', 'usernamehere''

http://msdn.microsoft.com/en-us/library/ms174378.aspx