When logging to kde in with my normal (non-root) ID, about 1 time in 2 the login hangs with a movable mouse but nothing on the screen and no activity possible. I can do Ctrl-alt-F1, log in as root, 'telinit 3', 'telinit 5', and have another try at logging in.
This is happening with OpenSUSE Leap 42.3 and 42.2 .
I find the following in /var/log/kdm.log :

X.Org X Server 1.18.3
Release Date: 2016-04-04
X Protocol Version 11, Revision 0
Build Operating System: openSUSE SUSE LINUX
Current Operating System: Linux linux-id8p 4.4.68-2-default #1 SMP Tue May 16 15:52:17 UTC 2017 (a50dbcb) x86_64
Kernel command line: BOOT_IMAGE=/vmlinuz-4.4.68-2-default root=/dev/mapper/vg_tjcw200-lv_root resume=/dev/vg_tjcw2/lv_swap splash=silent quiet showopts resume=/dev/vg_tjcw2/lv_swap splash=silent quiet showopts resume=/dev/vg_tjcw2/lv_swap splash=silent quiet showopts resume=/dev/vg_tjcw2/lv_swap splash=silent quiet showopts
Build Date: 28 May 2017  04:37:20PM

Current version of pixman: 0.34.0
        Before reporting problems, check http://wiki.x.org
        to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting,
        (++) from command line, (!!) notice, (II) informational,
        (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/var/log/Xorg.0.log", Time: Fri Jun  2 16:23:03 2017
(==) Using config directory: "/etc/X11/xorg.conf.d"
(==) Using system config directory "/usr/share/X11/xorg.conf.d"
klauncher(11690) kdemain: No DBUS session-bus found. Check if you have started the DBUS server.
kdeinit4: Communication error with launcher. Exiting!
kdmgreet(11684)/kdecore (K*TimeZone*): KSystemTimeZones: ktimezoned initialize() D-Bus call failed:  "Not connected to D-Bus server"

kdmgreet(11684)/kdecore (K*TimeZone*): No time zone information obtained from ktimezoned
(II) AIGLX: Suspending AIGLX clients for VT switch