As a workaround that was published in several threads, e.g.
one can terminate the X-Server automatically with every logout, so it has to restart with the login. Uncomment the line
in the kdmrc (with kde4 and SuSE located in /usr/share/kde4/config/kdm). Do this if necessary for multi-seat configurations with every [X-:?-Core] section in kdmrc.
This solved the problem for me for the time being.