Looks like perhaps you haven't set your permissions to allow anyone to add records.

There is a great tutorial on JPDeni's site which includes a section on setting permissions (with a chart).
http://www.jpdeni.com/dbman

If that doesn't help, please post a .txt file copy of your .cfg file and state what permissions you want to allow for your database and someone can help you.

Unoffical DBMan FAQ

http://creativecomputingweb.com/dbman/index.shtml/