I have a couple of VirtualBox ubuntu VMs with Guest Additions installed: 16.04, 16.10, 17.10, all of them work fine prior to upgrade. In fact, I just did a do-release-upgrade yesterday from 16.10 to 17.10 and everything works fine.
Today, seeing that 18.04 LTS has been released, I upgraded two of my 17.10, and both of them failed to boot after upgrade. They flash 4 times between the small verbose boot sequence screen and a full screen black screen before freezing. Both of them have very similar failure.
I attempted to hold shift during boot to enter recovery and command prompt to
sudo apt-get remove virtualbox-*
but the problem persists.
My host is 64-bit Windows 7 Ultimate on a Z77 platform with a nVidia GTX 750 Ti graphics card. VirtualBox version 5.2.8 r121009 with Extension Pack installed.