You can do one of two things of your choice: in the console as root, type dpkg remove --purge libpam-runtime libpam0g libpam0g-dev or you can type dpkg --force-overwrite libpam-runtime libpam0g libpam0g-dev. One will remove the faulty packages and the other will force it in. Personally, I'd rather remove the packages and then apt-get -s -t unstable libpam-runtime to see if it takes first before going thru with the install.

HTH,

Durand