I have fixed this issue. The fix can be seen here: https://forums.virtualbox.org/viewtopic.php?f=35&t=82639

If on a Linux host, are you a member of the 'vboxusers' group? If not, add yourself with the following command and then reboot your host, or logout and login to activate the change in group membership:

    sudo usermod -a -G vboxusers <your_username>