Thanks for your comments so far. The problem is I'm not trying to use a development edition; this problem first occurred when clicking on the "update" icon (top right of the screen). It also still occurs when I just run sudo update-manager -c
In all cases, I end up being told I require a distribution upgrade, and then that fails because it can't calculate the update. I just want to get back on the main path - do I have any options at all, or do I have to reinstall from scratch? -- Update Manager could not calculate upgrade https://launchpad.net/bugs/80988 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
