This has started to happen after I encrypted my home folder (this was done after the installation, not as a part of it)... This was in 11.10.
I have since upgraded to 12.04 and after first reboot everything worked well. However since reboot after this, the messages started to pop up again before the actual KDM login prompt.
I am using Kubuntu 12.04 and I have tried different things such as permissions 777 for /tmp, removing everythign from /tmp or even deleeting ~/.kde or ~/.Xauthority etc.