I couldn't find any information on this issue, so when I solved it I thought I would post it and the answer on AskUbuntu in case anyone else has the same issue.
Virtualbox refused to start any virtual machines; told me to run
/etc/init.d/vboxdrv setup as root. Doing so resulted in:
Stopping VirtualBox kernel modules ...done. Uninstalling old VirtualBox DKMS kernel modulesError! Could not locate dkms.conf file. File: does not exist. ...done. Trying to register the VirtualBox kernel modules using DKMSError! DKMS tree already contains: vboxhost-4.3.18 You cannot add the same module/version combo more than once. ...failed! (Failed, trying without DKMS) Recompiling VirtualBox kernel modules ...failed! (Look at /var/log/vbox-install.log to find out what went wrong)