So this seems to be a KDE update issue. kde4 doesn't seem to exist any more after the update. So the DEFAULT_WM is set to an invalid parameter. We do rely on this to be set correctly however. We could add even more sanity checks and replace the WINDOWMANAGER with a default when it is obvious that the value in /etc/sysconfig/windowmanager is bogus to ... maybe twm? This ought to be an incentive to fix this ;)