Seems the postinst didn't run for software-center during install.  Purging software-center and installing the package again does correct the problem, but we need to get to the root cause of the failure in the installer.

Here is a chunk of the log from the installer:

Aug 18 14:58:19 ubuntu ubiquity: Processing triggers for software-center ...
Aug 18 14:58:19 ubuntu ubiquity: No protocol specified
Aug 18 14:58:19 ubuntu ubiquity: /usr/lib/pymodules/python2.6/gtk-2.0/gtk/__init__.py:57: GtkWarning: could not open display
Aug 18 14:58:19 ubuntu ubiquity:   warnings.warn(str(e), _gtk.Warning)
Aug 18 14:58:19 ubuntu ubiquity: Traceback (most recent call last):
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/sbin/update-software-center", line 33, in <module>
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: from softwarecenter.enums import *
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/share/software-center/softwarecenter/__init__.py", line 21, in <module>
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: from db.application import Application
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/share/software-center/softwarecenter/db/application.py", line 31, in <module>
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: from softwarecenter.backend import get_install_backend
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/share/software-center/softwarecenter/backend/__init__.py", line 22, in <module>
Aug 18 14:58:19 ubuntu ubiquity:     backend = AptdaemonBackend()
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/share/software-center/softwarecenter/backend/aptd.py", line 97, in __init__
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: TransactionsWatcher.__init__(self)
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/share/software-center/softwarecenter/backend/transactionswatcher.py", line 33, in __init__
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: bus = dbus.SystemBus()
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/lib/pymodules/python2.6/dbus/_dbus.py", line 202, in __new__
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: private=private)
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/lib/pymodules/python2.6/dbus/_dbus.py", line 108, in __new__
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: bus = BusConnection.__new__(subclass, bus_type, mainloop=mainloop)
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/lib/pymodules/python2.6/dbus/bus.py", line 125, in __new__
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: bus = cls._new_for_bus(address_or_type, mainloop=mainloop)
Aug 18 14:58:19 ubuntu ubiquity: dbus.exceptions
Aug 18 14:58:19 ubuntu ubiquity: .
Aug 18 14:58:19 ubuntu ubiquity: DBusException
Aug 18 14:58:19 ubuntu ubiquity: :
Aug 18 14:58:19 ubuntu ubiquity: org.freedesktop.DBus.Error.FileNotFound: Failed to connect to socket /var/run/dbus/system_bus_socket: No such file or directory
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: Error in sys.excepthook:
Aug 18 14:58:19 ubuntu ubiquity: Traceback (most recent call last):
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/lib/python2.6/dist-packages/apport_python_hook.py", line 105, in apport_excepthook
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: os.O_WRONLY|os.O_CREAT|os.O_EXCL, 0600), 'w')
Aug 18 14:58:19 ubuntu ubiquity: OSError
Aug 18 14:58:19 ubuntu ubiquity: :
Aug 18 14:58:19 ubuntu ubiquity: [Errno 2] No such file or directory: '/var/crash/_usr_share_software-center_update-software-center.0.crash'
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: Original exception was:
Aug 18 14:58:19 ubuntu ubiquity: Traceback (most recent call last):
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/sbin/update-software-center", line 33, in <module>
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: from softwarecenter.enums import *
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/share/software-center/softwarecenter/__init__.py", line 21, in <module>
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: from db.application import Application
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/share/software-center/softwarecenter/db/application.py", line 31, in <module>
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: from softwarecenter.backend import get_install_backend
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/share/software-center/softwarecenter/backend/__init__.py", line 22, in <module>
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: backend = AptdaemonBackend()
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/share/software-center/softwarecenter/backend/aptd.py", line 97, in __init__
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: TransactionsWatcher.__init__(self)
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/share/software-center/softwarecenter/backend/transactionswatcher.py", line 33, in __init__
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: bus = dbus.SystemBus()
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/lib/pymodules/python2.6/dbus/_dbus.py", line 202, in __new__
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: private=private)
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/lib/pymodules/python2.6/dbus/_dbus.py", line 108, in __new__
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: bus = BusConnection.__new__(subclass, bus_type, mainloop=mainloop)
Aug 18 14:58:19 ubuntu ubiquity:   File "/usr/lib/pymodules/python2.6/dbus/bus.py", line 125, in __new__
Aug 18 14:58:19 ubuntu ubiquity:
Aug 18 14:58:19 ubuntu ubiquity: bus = cls._new_for_bus(address_or_type, mainloop=mainloop)
Aug 18 14:58:19 ubuntu ubiquity: dbus.exceptions
Aug 18 14:58:19 ubuntu ubiquity: .
Aug 18 14:58:19 ubuntu ubiquity: DBusException
Aug 18 14:58:19 ubuntu ubiquity: :
Aug 18 14:58:19 ubuntu ubiquity: org.freedesktop.DBus.Error.FileNotFound: Failed to connect to socket /var/run/dbus/system_bus_socket: No such file or directory
Aug 18 14:58:19 ubuntu ubiquity: