Oracle VirtualBox wouldn’t start, with this error:
Failed to acquire the VirtualBox COM object. The application will now terminate.Callee RC%3ANS_ERROR_FAILURE (0x80004005)
(Text may not be exact).
Fixed by doing this:
cd ~/.config/VirtualBox/
mv VirtualBox.xml VirtualBox.xml.original
cp VirtualBox.xml-prev VirtualBox.xml-prev.backup
mv VirtualBox.xml-prev VirtualBox.xml