How to fix the "Unable to calculate upgrade" issue when upgrading from 12.04 to 12.10?

As stated here , removing PPA sources does not work every time.

You need to uninstall offending packages. you can find them with:

grep Broken /var/log/dist-upgrade/apt.log

Mine was an xorg package. I removed it with the command:

sudo apt-get remove xserver-xorg-video-all

and then the upgrade could continue.

For a "NonPainful" release upgrade.

• Before proceed, check if the new release is available for upgrade. Open a terminal and give this command

  do-release-upgrade -c

If yes, proceed:

• Remove all the external PPAs you've added.

  From Software-Center > Edit > Software Sources > Other Software. Do not only un-tick ,but delete them.

• Then close all the graphical applications and open only a terminal.(Fullscreen is better) Give the bellow commands

  sudo apt-get update 
  sudo apt-get dist-upgrade
  

• Then give the bellow commands to do a little housekeeping

  sudo apt-get --purge autoremove
  sudo apt-get autoclean
  sudo apt-get purge $(dpkg -l | awk '/^rc/ { print $2 }')
  

• Then you can procceed with the upgrade

  sudo do-release-upgrade
  

Do not navigate or open windows or programs during the upgrade.

Be patient until the upgrade finish.

Friendly: Do not run (or rush) to upgrade from the day one. Upgrade from the day two or three(better).

I fixed mine by removing ppa packages I had installed using ppa-purge

I knew I needed to do this by checking the logs in /var/log/dist-upgrade/ at the end of the apt.log file youll see what was confusing it. In mine it was a video driver, and i was running several upgrades, so I did:

sudo ppa-purge ppa:ubuntu-x-swat/x-updates
sudo ppa-purge ppa:unity-team/staging
sudo ppa-purge ppa:webapps/preview
sudo ppa-purge ppa:nilarimogard/webupd8
sudo ppa-purge ppa:scopes-packagers/ppa
sudo ppa-purge ppa:glasen/intel-driver

the last one - the glasen driver - seems to have done the trick for me. Upgrade is now proceeding as normal.