After an upgrade to KDE 4.11.3, my Kubuntu 13.10 ceased to login to KDE. There would be a login loop (login, black screen, return to lightdm login).
I did attempt to go over other solutions such as fixing ~/.Xauthority, ~/.kde moving, changing permissions in my home folder to my own, there was no resolution.
I tried to see if I could try to login as another user, and I created one and attempted it. The issue still existed. So it wasn't directly due to my user thereby.
My next try was to see if there was a workspace issue with KDE's upgrade. I tried to login with the session set to "compiz-fusion" . This let me login to the Desktop but I had to execute "kwin --replace" to get my desktop back to normal. After repeated attempts at logouts an logins, this is the only workaround I have until I can find the culprit. I just want to directly login to my KDE Plasma Workspace and not have to manually start kwin and/or plasma/desktop.