oscommerce admin area doesn't work after install

Installed oscommerce 2.2rc2 via the installer and all seems to work fine until accessing the admin area. When I go to /oscommerce/admin it tells me there is no admin user. I enter the details admin/password and click create. It returns me to the login form where if I try and login with those details it doesn't work.

On checking the database table 'administrators' it's created a hashed password but the username column is blank. If I update the username column to admin and try the admin/password combination it again says invalid login.