You would have to MD5 encrypt the passwords when comparing them to the database fields in order to compare apples to apples.
Are you able to access tables from other interfaces? The database panel or Recordset definitions?
If the wizard can't recognize the tables, that is usually an issue with the site definition root url or with the database connection file. You can debug that by opening the database connection and testing it to see if it generates an error.
If you attach a copy of the login page I might be able to suggest where to update the md5 encryption manually.