Comment 14 for bug 710144

This helps for me: http://forum.kde.org/viewtopic.php?f=66&t=91936

1) Set in /etc/kde4/kdm/kdmrc AutoLoginEnable = false
2) reboot
3) select default session as kde

At login you'll get the following message:
"Your saved Gnome session isn't valid anymore.
Please, choose a new one or the default one will be used"