software-properties-gtk crashed with AttributeError in toggle_source_use(): 'NoneType' object has no attribute 'disabled'

[hernan]

source sortware crash on start

ProblemType: Crash
DistroRelease: Ubuntu 12.04
Package: software-properties-gtk 0.81.13.1
ProcVersionSignature: Ubuntu 3.1.0-2.3-generic 3.1.0
Uname: Linux 3.1.0-2-generic i686
ApportVersion: 1.26-0ubuntu1
Architecture: i386
CasperVersion: 1.290
Date: Sun Nov 13 17:43:48 2011
ExecutablePath: /usr/bin/software-properties-gtk
InterpreterPath: /usr/bin/python2.7
LiveMediaBuild: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha i386 (20111103)
PackageArchitecture: all
ProcCmdline: /usr/bin/python /usr/bin/software-properties-gtk -n -t 0
PythonArgs: ['/usr/bin/software-properties-gtk', '-n', '-t', '0']
SourcePackage: software-properties
Title: software-properties-gtk crashed with AttributeError in toggle_source_use(): 'NoneType' object has no attribute 'disabled'
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm admin audio cdrom dialout dip fax floppy fuse lpadmin netdev plugdev sambashare scanner tape video

[Apport retracing service (apport)]

Thank you for taking the time to report this crash and helping to make this software better. This particular crash has already been reported and is a duplicate of bug #854818, so is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Please continue to report any other bugs you may find.