Bug#619171: Update & Solution
I found the problem.
Hence the issue is very, very strange and probably only affects me, I suggest
closing it without any further investigation.
All tested KDE applications worked fine in Gnome, only starting K3b produced
"k3b: error while loading shared libraries: libGLU.so.1: cannot open shared
object file: No such file or directory".
So I looked in /usr/lib what's going on, but there was no libGLU.so.1!
A "dpkg --list | grep libglu1" produced:
ii libglu1-mesa 7.10-4
ii libglu1-mesa-dev 7.10-4
Because there was no bug report about missing libGLU I did a
"apt-get --reinstall install libglu1-mesa".
Afterwards the libGLU.so.1 was back and now my KDE is starting without
any problems since two days. No more segmentation faults.
I don't know who delete the lib. I did nothing manual in /usr/lib,
all my packages are up-to-date and there are no broken packages.
So it's just strange and I can't reproduce how my system came into