No Upgrades from Precise Pangolin to Quantal Quetzal?
Interestingly, the last Ubuntu upgrade had an interesting side effect. Even while always upgrading with sudo do-release-upgrade for each consecutive release, the upgrade to Precise Pangolin has set the default for such upgrades to LTS only. So in order to upgrade to Quantal Quetzal, this setting must be reversed. In order to do so easily the setting for prompt in /etc/update-manager/release-upgrades must be changed from lts to normal
I hope this value is in future not overwritten every time a normal upgrade to an LTS release is performed!