4
ok, then maybe check your database.
Look for the database table called [xoopsprefix]_users
See if there is a field called 'loginname'.
If it's there, then check to see whether it's empty for the webmaster user. If it's empty, put your user name in that field.
If the loginname field is missing altogether you could make a temporary one, just to get through the login process.
lets first see if that's necessary...