Comment 2 for bug 1615363

I reproduced this in Virtualbox using a Ubuntu MATE 16.04 LTS host:

Same iso: ubuntu-mate-16.04.1-desktop-amd64.iso
Same VM settings: 2GB RAM, No network connector.
Same partition layout: no swap, only "/" partition using entire 16GB dynamic size disk

ouroumov@Box:~/Desktop$ apt-cache policy virtualbox
virtualbox:
  Installed: 5.0.18-dfsg-2build1
  Candidate: 5.0.24-dfsg-0ubuntu1.16.04.1
  Version table:
     5.0.24-dfsg-0ubuntu1.16.04.1 500
        500 http://fr.archive.ubuntu.com/ubuntu xenial-updates/multiverse amd64 Packages
 *** 5.0.18-dfsg-2build1 500
        500 http://fr.archive.ubuntu.com/ubuntu xenial/multiverse amd64 Packages
        100 /var/lib/dpkg/status

See attachment for graphics bug screenshot.

Note: Switching to tty1 using (left control key + F1) then using "sudo systemctl restart lightdm.service" allows me to work around this issue and lands me on the correct login screen.