Thanks a lot Jean-Baptiste! I can reproduce the problem now. The ps afx output shows that the one process is in "dpkg-preconfigure" state while the other one is trying to install. So its indeed broken locking.
Thanks a lot Jean-Baptiste! I can reproduce the problem now. The ps afx output shows that the one process is in "dpkg-preconfigure" state while the other one is trying to install. So its indeed broken locking.