Comment 15 for bug 782953

Yes, this needs to be sorted out.

I was looking at the source code of the software-properties package and I may have found the problem.
In the file softwareproperties/gtk/SoftwarePropertiesGtk.py there is this method around line no. 991 (sorry if I'm not supposed to put code here):

    def on_close_button(self, widget):
        """Show a dialog that a reload of the channel information is required
           only if there is no parent defined"""
        if (self.modified_sourceslist == True and
                self.options.no_update == False):
            d = DialogCacheOutdated(self.window_main,
                                    self.datadir)
            d.run()
        self.quit()

This is where the program should ask the user if he wants to update the cache (the Kde version should have something similar), but that is not happening.
If I remove the "self.modified_sourceslist == True" part of the condition, it works, so I believe that variable is not set correctly (I suppose this variable should "tell" if the sources were changed).
I'm not an expert in Python, so it would be better if someone else checked this.

Now, for the Software Center, I haven't tested if it's still necessary to re-open it.