After the most recent upgrade performed on Saturday, June 3, 2017, I found that none of my VIrtualBox machines would start. A search on Google rendered me buried in too much information with the supposedly most-promising potential causes proving to not be the cause. I eventually just created a new machine using an existing machine image (*.vdi). I then started modifying the default configuration. See Oracle VM VirtualBox Manager -> Settings. The bottom line is that I found and isolated the one issue as root cause.
Oracle VM VirtualBox Manager -> Settings -> Display -> Acceleration: disable 3D acceleration.
Enabling 3D acceleration always worked before, but not now. I'm running an AMD graphics card, so there might be an issue with the non-proprietary driver or Baud-knows what else. The bottom line is that it works now.
