Up to version 3.0.0, SuperNZB used a different format for its database file. In order to upgrade to a more-recent version of the program, you can re-enter your data (of which there is not very much), or you can follow the database-file conversion process here.
To simply re-enter your server info, remove the SuperNZB.sdb database file from your SuperNZB folder. SuperNZB will then act as if it were being run for the first time.
To convert your existing SuperNZB.sdb database file, click here to download the conversion program. Once you have it, open the DMG and drag the ConvertSuperNZB.app program to your existing SuperNZB folder. Start the program and follow the on-screen instructions.