Virtualbox: NS_ERROR_FAILURE (0x80004005)
EDIT: I think I’ve worked out the problem, which makes it not related to the update. I used Windows yesterday (fastboot not enabled, and not dual-boot), which I guess made the HDDs read only. As a knock-on effect of that, the Virtual Box images were also read-only, which may have prevented VB from working properly. I logged into Windows and then restarted the PC. VB is working again and the drives are no longer read only.
This was an issue in a previous update, now back again. Rebooting had no effect.
My user is in the vboxusers group:
I also ran the command: sudo usermod --append --groups vboxusers lee as suggested in the 30th Dec 2020 stable update announcement (older issues).
I also removed and then reinstalled the latest extensions pack form the official site.