Software sources properties refuse to load with faulty repos in list

[Svein Tore]

1) I added the Fazena repo and I'm using Quantal. There are no files for Quantal there in the repo. Running sudo apt-get update hence gives me error messages.
2) I want to fix the added ppa lines, so I start Software Center and click Software Sources.

What happens:
Software sources tries to update the database. Naturally, it fails just like apt-get update. An error message is displayed containing:

W:Failed to fetch http://ppa.launchpad.net/tiheum/equinox/ubuntu/dists/quantal/main/source/Sources 404 Not Found
, W:Failed to fetch http://ppa.launchpad.net/tiheum/equinox/ubuntu/dists/quantal/main/binary-amd64/Packages 404 Not Found
, W:Failed to fetch http://ppa.launchpad.net/tiheum/equinox/ubuntu/dists/quantal/main/binary-i386/Packages 404 Not Found
, E:Some index files failed to download. They have been ignored, or old ones used instead.

Upon clicking ok, the message disappears, but nothing more happens. The software source window is never launched.

What I expect to happen:
After the error message, the window should still load, letting me fix the faulty lines.

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: software-properties-common 0.91
Uname: Linux 3.4.0-030400-generic x86_64
ApportVersion: 2.4-0ubuntu3
Architecture: amd64
Date: Thu Jul 19 18:08:42 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=nb_NO:nb:no_NO:no:nn_NO:nn:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=nb_NO.UTF-8
 SHELL=/bin/bash
SourcePackage: software-properties
UpgradeStatus: Upgraded to quantal on 2012-07-18 (0 days ago)

[Leon (lehjr)]

I had the same issue with a freshly installed and updated daily build from July 20th, but it turned out the issue was already reported as bug #1026066 (https://bugs.launchpad.net/ubuntu/+source/software-properties/+bug/1026066). However, this may not be the same issue you are having.

[Christopher (soft-kristal)]

I won't launch at all for me using 3.5.0-13 both 32 and 64 bit AMD systems.