My FreeBSD guest (8GB RAM, 32-bit with PAE enabled) came up almost as before. The X11-server started up and so did the window manager (XFCE4) and a couple of xterms. However, some other programs (including gvim) would not start complaining:
In an attempt to resolve this error I:OpenGL Warning: Failed to connect to host. Make sure 3D acceleration is enabled for this VM.
- upgraded the Virtual Box itself (from 5.x) to 6.0.10 -- including the "Extension Pack" -- on the host
- I then also upgraded the "OSE additions" inside the guest (from 5.2.30 to 5.2.32).
How do I fix this problem? Thanks!