virtualbox.org

I just got the same problem with a windows 10 host running Centos 7 Linux guest.
My virtualbox is 6.1.14 and has the matching guest extensions installed. It ran for about a week before this happened.
It is interesting that it happened right after a Windows 10 patch was installed! Maybe that latest patch is interfering with the virtualbox environment? Hopefully this will help the community find the root cause.

Hyper-V is enabled and needs to be disabled. See HMR3Init: Attempting fall back to NEM (Hyper-V is active). (The new test builds might have a fix for this problem. If you try a test build and it works, report here: viewtopic.php?f=6&t=90853, and save the installer file.)