Just to add some more detail. /etc/vbox/vbox.cfg *should* be installed by virtualbox-ose (found using dpkg -S /etc/vbox/vbox.cf), but I don't know how to force it to install. Running sudo aptitude reinstall virtualbox-ose does not regenerate this file.
In order to get working eventually I had to manually extract the vbox.cfg file from the virtualbox-ose deb package, and copy it over myself.
Just to add some more detail. /etc/vbox/vbox.cfg *should* be installed by virtualbox-ose (found using dpkg -S /etc/vbox/vbox.cf), but I don't know how to force it to install. Running sudo aptitude reinstall virtualbox-ose does not regenerate this file.
In order to get working eventually I had to manually extract the vbox.cfg file from the virtualbox-ose deb package, and copy it over myself.