Message "Call to lnusertemp failed (temporary directories full?). Check your installation?" displayed in X before KDM

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.

Any ideas?

I had the same issue and found that my /home/USER/.kde folder was owned by root, which was causing permissions issues. After fixing the ownership issues with 'chown', things worked as expected.

Do this in terminal:

cd ~/
sudo chown -R <user> .kde

I could login after renaming my ~/.kde folder. Apparently something was corrupted and renaming the folder causes creation of a clean version. You will probably loose settings but at least you can login.