Comment 9 for bug 850937

Found a solution for my setup. Root cause was an inconsistent installation, so I blame it at the package managements failure to clean up its own mess.

Anyhow, unity-greeter needs gnome-settings-daemon (or something along that line), I am actually having at xubuntu install without that.

My solution:
 - purged everything unity and lightdm (dpkg --purge --force-all ...)
 - remove /etc/lightdm, /var/lib/lightdm and /var/log/lightdm
 - reinstalled lightdm (apt-get -f install)
 - fix ownership of /var/log/lightdm (needs to be owned by lightdm otherwise x-0-greeter.log can't be written ... is anyone actually testing that stuff?)
 - and finally change 'greeter-session' in /etc/lightdm/lightdm.conf to lightdm-gtk-greeter.