@Adolfo, that was it! For some reason gnome-settings-daemon was uninstalled on my upgrade to 16.04, and on boot Ubuntu was complaining about an error with it. I installed it, re-logged in and everything is now correct.
@Adolfo, that was it! For some reason gnome-settings- daemon was uninstalled on my upgrade to 16.04, and on boot Ubuntu was complaining about an error with it. I installed it, re-logged in and everything is now correct.