Some days ago I upgraded my Sid system and when I restarted my X session the other day, I wasn't able to successfully login to KDE via kdm anymore. I'm getting some errors in ~/.xsession-errors:
kdeinit4: preparing to launch /usr/bin/knotify4
Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)knotify(16474) KNotify::event: 1 ref= 0
QMetaObject::invokeMethod: No such method KUniqueApplication::loadCommandLineOptionsForNewInstance()kdeinit4: preparing to launch /usr/bin/plasma-desktop
kded4: Fatal IO error: client killedkdeinit4: Fatal IO error: client killed
kdeinit4: sending SIGHUP to children.
klauncher: Exiting on signal 1
At the user/password prompt of kdm I can login, the KDE splash screen appears and then, suddenly, the connection fails and I'm back at the kdm login again.
I tried to look for already existing bug reports, but KDE is quite large and with many programs. Are there any pointers for a bug report or even a solution/fix for the problem, dear LazyWeb?
Sune suggests in the comments that it might be a Xorg problem. I've attached a xorg.txt logfile to this post. As you can see, there's a backtrace because of a sig11 error. Funny enough, when I connect via remote X from my OSX I can login into KDE, although there are visual errors. Xorg is working fine on the local server with Gnome, though. So, for me it seems related to either KDE or maybe Compiz.
Problem solved! LL hinted in the comments to reinstall the Nvidia driver and now it works again! Thanks! :-)