I'm running Manjaro 64 bit stable with KDE, and it worked fine until the last upgrade a few days ago (I believe it was Thursday). Then, KDE wouldn't start any more. I followed some suggestions (doing a full upgrade from the terminal with
pacman -Syyuu, which I did, and firefox was then updated, but that was it. After that I tried starting KDE from the terminal using
startx, which worked, but only to that extent, that the programs which I was using popped up and were distributed on the virtual desktops as always (and as desired earlier), but no KDE panel visible, so I couldn't switch between virtual desktops except for the first six ones with the help of keyboard shortcuts. I found out that systemsettings crashed as well as plasmashell when calling them from a terminal. I cannot run Alt-F2 or Alt-Space to call krunner, it simply doesn't work. Luckily I always have a terminal open on desktop 4, so I can use that to start up programs, but I would very much prefer to be able to move around using the panel.
Calling plasmashell from the terminal results in these lines:
org.kde.plasmaquick: Applet preload policy set to 1 libEGL warning: DRI2: failed to authenticate file:///usr/share/plasma/plasmoids/org.kde.desktopcontainment/contents/ui/main.qml:62:5: Unable to assign [undefined] to int file:///usr/share/plasma/plasmoids/org.kde.desktopcontainment/contents/ui/main.qml:53:5: Unable to assign [undefined] to int trying to show an empty dialog file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Desktop.qml:146:19: QML Loader: Binding loop detected for property "height" file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Desktop.qml:146:19: QML Loader: Binding loop detected for property "height" KCrash: Attempting to start /usr/bin/plasmashell from kdeinit sock_file=/run/user/1000/kdeinit5__1 KCrash: crashing... crashRecursionCounter = 2 KCrash: Application Name = plasmashell path = /usr/bin pid = 6546 KCrash: Arguments: /usr/bin/plasmashell KCrash: Attempting to start /usr/lib/drkonqi from kdeinit sock_file=/run/user/1000/kdeinit5__1 QSocketNotifier: Invalid socket 8 and type 'Read', disabling... QSocketNotifier: Invalid socket 9 and type 'Read', disabling... + Stopped plasmashell