Comment 19 for bug 1292398

this is probably related to this bug:

I'm not yet sure which is cause vs effect, but doing:

$ sudo cp ~/.config/monitors.xml /etc/gnome-settings-daemon/xrandr/

caused lightdm to start with the 'correct' monitor configuration for me. Sadly, it did not persist through login to gnome-shell, but

$ nohup gnome-settings-daemon -r

seems to fix it for my user session.