Comment 2 for bug 1360851

Ubuntu 12.10 reached End of Life (EOL) on May 16, 2014 and is no longer supported. In order to continue using it (not recommended because of potential security issues), you need to change your apt sources to point to http://old-releases.ubuntu.com/ubuntu/
If you need help doing that, please use a support resource, such as https://answers.launchpad.net/ubuntu or the sites suggested at http://community.ubuntu.com/help-information/

If you don't like to upgrade often, a fresh install of Ubuntu 14.04 LTS is highly recommended, since it will be supported until 2019.