A clue: The file /usr/lib/python2.7/dist-packages/UpdateManager/Core/DistUpgradeFetcherCore.py seems to be where the decision-making happens. And it seems to depend in very particular ways on the contents of /etc/apt/sources.list. Unfortunately I just don't know enough about the context to analyze this any further. It does seem that if /etc/apt/sources.list is not quite in the form that this program is expecting, the upgrade won't be found. But I can't tell just what it's looking for. if it helps, here's the contents of my /etc/apt/sources.list: ############################################################# ################### OFFICIAL UBUNTU REPOS ################### ############################################################# ###### Ubuntu Main Repos deb http://us.archive.ubuntu.com/ubuntu/ precise main restricted universe multiverse deb-src http://us.archive.ubuntu.com/ubuntu/ precise main restricted universe multiverse ###### Ubuntu Update Repos deb http://us.archive.ubuntu.com/ubuntu/ precise-security main restricted universe multiverse deb http://us.archive.ubuntu.com/ubuntu/ precise-updates main restricted universe multiverse deb http://us.archive.ubuntu.com/ubuntu/ precise-backports main restricted universe multiverse deb-src http://us.archive.ubuntu.com/ubuntu/ precise-security main restricted universe multiverse deb-src http://us.archive.ubuntu.com/ubuntu/ precise-updates main restricted universe multiverse deb-src http://us.archive.ubuntu.com/ubuntu/ precise-backports main restricted universe multiverse ###### Ubuntu Partner Repo deb http://archive.canonical.com/ubuntu precise partner deb-src http://archive.canonical.com/ubuntu precise partner ###### Ubuntu Extras Repo deb http://extras.ubuntu.com/ubuntu precise main deb-src http://extras.ubuntu.com/ubuntu precise main ############################################################## ##################### UNOFFICIAL REPOS ###################### ############################################################## ###### 3rd Party Binary Repos #### Audacity - http://audacity.sourceforge.net/ ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys BB901940 deb http://ppa.launchpad.net/audacity-team/daily/ubuntu precise main #### Flacon - http://kde-apps.org/content/show.php?content=113388 ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys F2A61FE5 deb http://ppa.launchpad.net/flacon/ppa/ubuntu precise main #### GetDeb - http://www.getdeb.net ## Run this command: wget -q -O- http://archive.getdeb.net/getdeb-archive.key | sudo apt-key add - deb http://archive.getdeb.net/ubuntu precise-getdeb apps #### Gimp - https://launchpad.net/~otto-kesselgulasch/+archive/gimp ## Run this command: sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 614C4B38 deb http://ppa.launchpad.net/otto-kesselgulasch/gimp/ubuntu precise main #### GNOME3 extra apps - https://launchpad.net/~gnome3-team/+archive/gnome3 ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 3B1510FD deb http://ppa.launchpad.net/gnome3-team/gnome3/ubuntu precise main #### GNUzilla and IceCat - http://www.gnu.org/software/gnuzilla/ ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys deb http://ppa.launchpad.net/gnuzilla-team/ppa/ubuntu precise main #### Google Chrome Browser - http://www.google.com/linuxrepositories/ ## Run this command: wget -q https://dl-ssl.google.com/linux/linux_signing_key.pub -O- | sudo apt-key add - deb http://dl.google.com/linux/chrome/deb/ stable main #### Google Earth - http://www.google.com/linuxrepositories/ ## Run this command: wget -q https://dl-ssl.google.com/linux/linux_signing_key.pub -O- | sudo apt-key add - #### Google Linux Software Repositories - http://www.google.com/linuxrepositories/ ## Run this command: wget -q https://dl-ssl.google.com/linux/linux_signing_key.pub -O- | sudo apt-key add - # deb http://dl.google.com/linux/deb/ stable non-free #### Jupiter - http://www.webupd8.org/2010/07/jupiter-ubuntu-ppa-hardware-and-power.html ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys EEA14886 deb http://ppa.launchpad.net/webupd8team/jupiter/ubuntu precise main #### Kubuntu Backports - https://edge.launchpad.net/~kubuntu-ppa/+archive/backports ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 8AC93F7A deb http://ppa.launchpad.net/kubuntu-ppa/backports/ubuntu precise main #### Kubuntu Updates - https://edge.launchpad.net/~kubuntu-ppa/+archive/ppa ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 8AC93F7A deb http://ppa.launchpad.net/kubuntu-ppa/ppa/ubuntu precise main #### LibreOffice - http://www.documentfoundation.org/download/ ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 1378B444 deb http://ppa.launchpad.net/libreoffice/ppa/ubuntu precise main #### Medibuntu - http://www.medibuntu.org/ ## Run this command: sudo apt-get --quiet update && sudo apt-get --yes --quiet --allow-unauthenticated install medibuntu-keyring && sudo apt-get --quiet update deb http://packages.medibuntu.org/ precise free non-free #### PlayDeb - http://www.playdeb.net/ ## Run this command: wget -O- http://archive.getdeb.net/getdeb-archive.key | sudo apt-key add - deb http://archive.getdeb.net/ubuntu precise-getdeb games #### qBittorrent - http://qbittorrent.sourceforge.net/ ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 47B4D1C4 deb http://ppa.launchpad.net/hydr0g3n/ppa/ubuntu precise main #### UAlinux - http://ualinux.com/ualinux-repo ## Run this command: wget -q -O- http://archive.ualinux.com/ualinux.key | sudo apt-key add - # deb http://archive.ualinux.com/ubuntu precise main #### Ubuntu Tweak - http://ubuntu-tweak.com/ ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 0624A220 deb http://ppa.launchpad.net/tualatrix/ubuntu precise main #### UNetbootin - http://unetbootin.sourceforge.net/ ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys FC91AE7E deb http://ppa.launchpad.net/gezakovacs/ppa/ubuntu precise main #### Wine - https://launchpad.net/~ubuntu-wine/+archive/ppa/ ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys F9CB8DB0 deb http://ppa.launchpad.net/ubuntu-wine/ppa/ubuntu precise main ####### 3rd Party Source Repos #### Kubuntu Backports (Source) - https://edge.launchpad.net/~kubuntu-ppa/+archive/backports ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 8AC93F7A deb-src http://ppa.launchpad.net/kubuntu-ppa/backports/ubuntu precise main #### Kubuntu Updates (Source) - https://edge.launchpad.net/~kubuntu-ppa/+archive/ppa ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 8AC93F7A deb-src http://ppa.launchpad.net/kubuntu-ppa/ppa/ubuntu precise main #### Medibuntu (Source) - http://www.medibuntu.org/ ## Run this command: sudo apt-get --quiet update && sudo apt-get --yes --quiet --allow-unauthenticated install medibuntu-keyring && sudo apt-get --quiet update deb-src http://packages.medibuntu.org/ precise free non-free #### UNetbootin (Source) - http://unetbootin.sourceforge.net/ ## Run this command: sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys FC91AE7E deb-src http://ppa.launchpad.net/gezakovacs/ppa/ubuntu precise main