Failed to request VPN secrets #2: (6) No agents were available for this request.
Google only pointed by to obscure old bug reports or the Arch Linux fix. But the Arch fix was of no use in Ubuntu. Until finally I stumbled upon a solution (which I have now lost track of). It's rather simple, but be careful!
sudo apt-get remove --purge network-manager-gnome
Now reboot. Hopefully you'll come back online but without the widget when logging back in. Then, just reinstall the package.
sudo apt-get install network-manager-gnome
As a precaution, you can download the package, just in case your network doesn't work without the user widget.
