Comment # 1 on bug 1002865 from Wolfgang Bauer

(In reply to Andreas Bock from comment #0)
> SDDM::GreeterApp(0x7ffff0524460), parent's thread is QThread(0x18360f0),
> current thread is QThread(0x1b54810)

I suppose this is about SDDM then, not kdm... ;-)

> The problem occured after yesterdays update to Tumbleweed 20160928
> I can reproduce the problem on both a hardware machine and a xen DomU

Hm, I just did a fresh Tumbleweed installation in VirtualBox today, and it
worked fine (except that Xorg didn't start at all with the vboxvideo driver,
not even via xdm or startx, that's a completely different problem though, after
uninstalling that it was "fixed").

Just for clarification: you get the black screen instead of the login screen,
or when you actually try to login?

If it's the latter, it would actually be a problem with the desktop you tried
to login to I suppose.

And related: do you have Auto-login enabled?

Do you get back to the login screen if you press Ctrl+Alt+Backspace twice?

Do you use any additional repos?