I've been using Ubuntu 12.04 for about 8 months. My machine was disconnected for a couple of weeks. Am now connected, and Update Manager has 23 updates waiting. But I get a warning "The action would require the installation of packages from not authenticated sources."
I've tried several, single updates, and so far all have this warning. E.g., for just the SSL development libraries, header files and documentation, the "Details" panel shows: libssl-dev
I see that a very similar question at my update manager say "Requires installation of untrusted packages" was answered in terms of terminal commands.
What is happening here? If I go the command-line route, must I abandon the Update Manager permanently?