Linux Mint 18.1 not booting - solved

Linux Mint was not booting into graphical mode. It was not even dropping me into an emergency shell - a dialog box about not being able to connect to upstart would appear, your session lasted only 10 seconds etc, and the window manager would restart. Initially I thought this was due to some problem related to booting as in my previous post. But then, saw this post on the Linux Mint forums. So, hit Ctrl Alt F2 to get a shell, (in my case, fn+Ctrl+Option, since this is a Macbook), did
  apt remove virtualbox-guest*
and rebooted OK.