Having upgraded my FreeBSD system and VirtualBox, I found that VirtualBox does not work when invoked from the window manager’s menu. So, I tried running it from the command line, and got the following message: /usr/local/lib/virtualbox/VirtualBox.so: Undefined symbol “_ZNK6QColor6darkerEi@Qt_5” I tried to search the web for the cause, and found a link to a compatibility …