The checkboxes that appear to be changeable under the Edit / Software Sources dialog box cannot be changed. I click on them and they just turn gray and stay at their current setting.
When I run software-center from a terminal window and try to change one of the checkbox settings, I get:
Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/softwareproperties/gtk/SoftwarePropertiesGtk.py", line 649, in on_isv_source_toggled self.backend.ToggleSourceUse(str(source_entry)) File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 143, in __call__ **keywords) File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 630, in call_blocking message, timeout) dbus.exceptions.DBusException: com.ubuntu.SoftwareProperties.PermissionDeniedByPolicy: com.ubuntu.softwareproperties.applychanges
These things happen instead of it properly prompting me for a password (for root privs).