This bug has been fixed as part of recent refactoring in this area. The latest version in Quantal, 5.3.14.2 contains this fix (as do prior versions). Many thanks for your help!
** Changed in: software-center (Ubuntu) Status: New => Fix Released -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to software-center in Ubuntu. https://bugs.launchpad.net/bugs/1044919 Title: software-center crashed with TypeError in function(): add_child() takes exactly 4 arguments (2 given) Status in “software-center” package in Ubuntu: Fix Released Bug description: Just appened after opening Software Center ProblemType: Crash DistroRelease: Ubuntu 12.10 Package: software-center 5.3.10 ProcVersionSignature: Ubuntu 3.5.0-13.14-generic 3.5.3 Uname: Linux 3.5.0-13-generic i686 ApportVersion: 2.5.1-0ubuntu4 Architecture: i386 Date: Sun Sep 2 09:52:49 2012 ExecutablePath: /usr/share/software-center/software-center InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Beta i386 (20120301) InterpreterPath: /usr/bin/python2.7 PackageArchitecture: all ProcCmdline: /usr/bin/python /usr/bin/software-center ProcEnviron: PATH=(custom, no user) LANG=it_IT.UTF-8 SHELL=/bin/bash PythonArgs: ['/usr/bin/software-center'] SourcePackage: software-center Title: software-center crashed with TypeError in function(): add_child() takes exactly 4 arguments (2 given) UpgradeStatus: Upgraded to quantal on 2012-08-31 (2 days ago) UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/software-center/+bug/1044919/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp