The error message indicates that there is a disparity between the extension and VirtualBox versions. This can be because either of them is outdated or the extension ...

If you encounter VirtualBox Error VERR_ALREADY_EXISTS, you should reboot the host computer before installing a fresh extension or a VM. Your system is most likely ...

What I've never quite understood is, given Oracle's mindset and history, why the hell haven't they screwed up VirtualBox completely? They were not good custodians of Solaris, Java, OpenOffice... yet, ...