Login screen does not re-appear after KDE logout

[gothbert]

Running Kubuntu 15.04. nightly build as at 21 Mar 2015
Using KDE start menu to logoff
After logoff the logon screen does not appear (black screen, still in X, since mouse arrow cursor visible and can be moved around)
Need to reboot

[gothbert (omega-y)]

I ran
   apport-collect 1435161
and got the message, that no additional information could be collected.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

To change the source package that this bug is filed about visit https://bugs.launchpad.net/ubuntu/+bug/1435161/+editstatus and add the package name in the text box next to the word Package.

[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]

[gothbert (omega-y)]

Additional finding: logging off actually does not log off the session. The window manager seems to go away but programs still are running - some even visible behind a dimmed screen.

[gothbert (omega-y)]

Additional finding:
- this occurs both for users with home directory on local drive and on NFS mounted filesystems
- this occurs also for a newly added user (only skeleton home directory)