How-to: Fix Untrusted Packages Error in Ubuntu 11.10
If you've added PPA's (Personal Package Archives) to your software sources in Ubuntu, you may find you get an error when you try to run updates in the Update Manager. ‘Requires installation of untrusted packages’ This is typically owing to missing GPG keys for those PPA's so that Update Manager can't verify those updates. It will simply refure to install those updates. It is easy to fix.