Perchè ubuntu software center si chiude improvvisamente??

Salve a tutti, ho da poco aggiornato ubuntu 12.04 a 13.10, ma il software center non si apre più, nemmeno provando a reinstallare. Provando ad avviare da terminale esce questo errore:

2013-07-13 11:13:51,865 - softwarecenter.ui.gtk3.app - INFO - setting up proxy 'None'
Traceback (most recent call last):
  File "/usr/bin/software-center", line 130, in <module>
    app = SoftwareCenterAppGtk3(options, args)
  File "/usr/share/software-center/softwarecenter/ui/gtk3/app.py", line 429, in __init__
    self.useful_cache = UsefulnessCache(True)
  File "/usr/share/software-center/softwarecenter/backend/reviews/__init__.py", line 91, in __init__
    self._retrieve_votes_from_server()
  File "/usr/share/software-center/softwarecenter/backend/reviews/__init__.py", line 105, in _retrieve_votes_from_server
    user = get_person_from_config()
  File "/usr/share/software-center/softwarecenter/utils.py", line 638, in get_person_from_config
    cfg = get_config()
  File "/usr/share/software-center/softwarecenter/config.py", line 180, in get_config
    _software_center_config = SoftwareCenterConfig(filename)
  File "/usr/share/software-center/softwarecenter/config.py", line 38, in __init__
    super(SoftwareCenterConfig, self).__init__()
TypeError: must be type, not classobj

cosa potrei fare per risolvere? grazie in anticipo.