Comment # 24 on bug 1013550 from Michael Hirmke

The notfication in this case comes from removing the clock applet. It should
show the "Undo" button. But in other cases, notifications for example from the
nm-applet also cause the hang.

Your kio packages have version 5.26.0-5.1, while my installed default openSUSE
versions already had 5.26.0-6.2. So I had to downgrade those two packages - was
that really, what you wanted me to do?

It didn't help, though:
I installed both packages and rebootet the system, but the error remained
unchanged 8-(