Out of nowhere, my Update Notifier has started showing up (orange icon in Gnome Panel) when I first log in. But there aren't any updates available. When I hover over the icon, I get:
A error occured, please run package manager from the right-click menu or apt-get on a terminal to see what is wrong. The error message was: 'Error: Opening the cache (E:Opening /etc/apt/sources.list - ifstream::ifstream (13 Permission denied), E:The list of sources could not be read.)
No error is reported when I run apt-get, or open synaptic. Nothing else appears broken, so it's really just an annoyance. I tried disabling my non-standard sources, and even reinstalled the update-manager and notifier. Still no change.