Upgrade to 12.10 from 12.04 not available in update manager

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http://askubuntu.com – My update manager does not give me the option to upgrade to Ubuntu 12.10. That is, the "New distribution release '12.10' is available. Click Upgrade and follow the on-screen instructions" section is not shown. I had the same problem upgrading to 12.04. Spent hours trying to upgrade the system, got lucky somehow, don’t definitively know how. What I have done, used Synaptic to clear package cache. reloaded package list and upgraded all packages. checked that ubuntu-standard and ubuntu-desktop packages are installed. checked that the "notify me of new version" setting in update-manager is (HowTos)