VirtualBox USB permission problem

On attempting to change USB settings for a virtual machine I got the following error in a popup dialog:

Result Code: NS_ERROR_FAILURE (0x00004005)

Component: Host
Interface: IHost {35b004f4-7806-4009-bfa8-d1308adba7e5}
Callee: IMachine {662c175e-a69d-40b8-a77a-1d719d0ab062}

Turns out that this error is the result of Kubuntu/Ubuntu not adding the default user to the vboxusers group.

You can check your groups by opening a terminal and running groups or using the users section of the KDE System Settings (or equivalent in Gnome) or kuser or whatever.

Adding yourself to a group is usually as easy as clicking the group, choosing to modify it and then adding your username to the list, for me there were no users listed. In a terminal you could do sudo usermod -aG vboxusers username where username is the name of your user (if you’re not sure it’s returned by whoami).