That's odd. I've never seen it fail like that before. First time for everything, I guess.
Rerun getvirtualbox. It should recreate the DKMS kernel module. Reboot immediately after VirtualBox is reinstalled. If there's a boot splash screen, press the Escape key at the prompt to see the boot messages and verify that a kernel module does build.
You won't have to reinstall any VMs, and the installation process won't erase any of them.