Every time you open a kde client, the startkde shell deletes every socket
files in /tmp/, including those opened by any other kde client.
Then, it's impossible to open any window from an kde panel.

You can easily solve that problem by deleting only the files corresponding
to your current display.

#for file in /tmp/kfm_* /tmp/kio* ; do

real_display=`echo $DISPLAY | sed "s/://" | sed "s/\..*//"`
for file in /tmp/kfm_*_$real_display /tmp/kio*_$real_display ; do
   if [ -O $file ]; then
        rm -fr $file
    fi
done