Fix is next:
Run this in terminal (providing a sudo password)
On next reboot it will not appear again.
Run this in terminal (providing a sudo password)
sudo
vi /etc/X11/Xsession.d/98vboxadd-xclient
find the linenotify-send
"VBoxClient: the VirtualBox kernel service is not running. Exiting."
Now change notify-send to echo
echo "VBoxClient: the VirtualBox kernel service is not running. Exiting."
And save the file.On next reboot it will not appear again.