[arch-general] shutdown problems

hi all, since a few days, i experience some problems on shutdown. i'm running kde and systemd on a fully upgraded system. when shutting down via kde controls (ctrl-alt-del oder button), i am logged off and presented the login screen, but no shutdown occurs. i tried to change the shutdown command from '/sbin/shutdown -h -p now' to '/sbin/shutdown -h now' but that made just no difference. if i use these commands on bash, it shuts down as expected, not showing the login screen. is this somewhat systemd-related? hints appreciated… georg