So you tried installing Ubuntu on your Mac's VirtualBox and got this error:
Failed to load VMMR0.r0 (VERR_SUPLIB_OWNER_NOT_ROOT).
There probably are many causes for this error, but the one I encountered was because of
/Applications not being owned by root.
To see who owns
$ ls -l /
If the owner of /Applications is not root:
$ sudo chown root
Try installing Ubuntu now. The problem should be gone. Happy virtual boxing!