2 more (Squeeze) systems to upgrade from 3.5.12 here today. Using official repo (not "nightly builds") I made sure to upgrade all Debian packages first (TDE sources temporarily disabled) and reboot. There was a recent Squeeze "point release". One machine has nvidia. Then (TDE sources re-enabled) used apt-get in download-only mode : apt-get update && apt-get dist-upgrade -d Once more: apt-get update && apt-get dist-upgrade -d That should have shown error messages for any failed downloads (there were not). If so I could have either waited or downloaded manually from "nightly builds" to /var/cache/apt/archives Then, to see if any other errors, like half the system to be removed or packages which apt will not install: apt-get dist-upgrade -s Finally, when satisfied it all looks good: (su) /etc/init.d/kdm-trinity stop (log in to shell as root) apt-get update && apt-get dist-upgrade (when prompted for config file overwrites, select "install the package maintainer's version") /etc/init.d/kdm-trinity start No problems at all.