It crashed after I asked it to enable universe, while it was installing another application. I was also going through the "sync from other computers" software list at the time.
ProblemType: Crash
DistroRelease: Ubuntu 12.04
Package: software-center 5.1.12
ProcVersionSignature: Ubuntu 3.2.0-18.28-generic 3.2.9
Uname: Linux 3.2.0-18-generic x86_64
ApportVersion: 1.94.1-0ubuntu1
Architecture: amd64
Date: Fri Mar 9 10:32:10 2012
ExecutablePath: /usr/share/software-center/software-center
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Beta amd64 (20120301)
InterpreterPath: /usr/bin/python2.7
PackageArchitecture: all
ProcCmdline: /usr/bin/python /usr/bin/software-center
ProcEnviron:
LANG=en_US.UTF-8
SHELL=/bin/bash
PythonArgs: ['/usr/bin/software-center']
SourcePackage: software-center
Title: software-center crashed with TypeError in function(): unknown type (null)
UpgradeStatus: Upgraded to precise on 2012-03-09 (0 days ago)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo
Status changed to 'Confirmed' because the bug affects multiple users.