This question has been addressed a number of times in the DBMAN Forums and most recently in the DBMAN Customization Forum yesterday. Search for default user.
The record has to be added to use fields from the default.db file. To pull the username from the default.pass, there are codes available via Modifications at the following web site:
http://www.jpdeni.com/dbman/
Which is also another good web site to check before asking questions in the forums!
Regards,
Eliot Lee