dpkg -i --force-overwrite /var/cache/apt/archives/lxpanel_0.7.2-1ubuntu1_i386.deb (see #4)
did not help in my case, but
dpkg -i --force-overwrite /var/cache/apt/archives/lxpanel-data_0.7.2-1ubuntu1_all.deb
indeed solved the problem -> the lxde desktop works properly again!
dpkg -i --force-overwrite /var/cache/ apt/archives/ lxpanel_ 0.7.2-1ubuntu1_ i386.deb (see #4)
did not help in my case, but
dpkg -i --force-overwrite /var/cache/ apt/archives/ lxpanel- data_0. 7.2-1ubuntu1_ all.deb
indeed solved the problem -> the lxde desktop works properly again!