Apt message d'erreur 
files list file for package `smbfs' is missing final newline

Well, with a big help from #debian at freenode, I found the solution (thanks justin!!):

the file /var/lib/dpkg/info/smbfs.list was corrupted, it was all binary crap. Dunno how this could happen, but it was. So justin advised me to delete the file (actually, I mv'd it) - and, voila, apt warned me that the files list could not be found for smbfs, but at least I could apt-get remove smbfs --purge and install it again (apt-get install smbfs) - that took the biscuit!