Hi, I have the problem with Mantis '1.0.0a3' that the field "Real Name" have to be set as unique but wie have two Thomas Kalinkas over here, so the Login is different but the names are the same.
There is a setting ($g_differentiate_duplicates) that can help by displaying the userid after a duplicate name. You need to enable it, then re-run the database upgrade to detect all of the existing duplicates.