Comment 36 for bug 976124

Sounds to me like there's a bug in your udev rules. Does:

    udevadm info --export-db

show the tags and ID_SEAT variable set like you expect?

Other comments:

  * You don't need a udev rule to assign something to seat0.
    Everything is assigned to seat0 by default.

  * Probably unrelated but you may need to enable
    'user-authority-in-system-dir' in your lightdm.conf:

        [SeatDefaults]
        user-authority-in-system-dir=true

  * I recommend against setting xserver-vt=7 for seat0 -- let LightDM
    choose the VT number for you.

  * You don't need to pass -sharevts to X for seat1 -- LightDM will do
    that for you.

If you are still unable to get it to work, please post additional
information:

  * output of 'udevadm info --export-db'
  * X logs
  * LightDM logs with debugging turned on (edit /etc/init/lightdm.conf
    and change 'exec lightdm' to 'exec lightdm -d')