When i try to open software center it opens but nothing shows up on the window and it closes after 5 seconds. it had worked previously and then i did a ppa purge and then it won't open. the ppa i tried to remove was ppa:sunab/kdenlive-release
after i purged that ppa the terminal said there was conflict. it offered me a solution (that i didn't read) and i accepted it. after it was done software center wouldn't open software-center

here is the output from the terminal

2013-04-18 11:56:47,034 - softwarecenter.ui.gtk3.app - INFO - setting up proxy 'None'

2013-04-18 11:56:47,050 - softwarecenter.db.database - INFO - open() database: path=None use_axi=True use_agent=True

2013-04-18 11:56:48,620 - softwarecenter.backend.reviews - WARNING - Could not get usefulness from server, no username in config file

2013-04-18 11:56:49,354 - softwarecenter.ui.gtk3.app - INFO - show_available_packages: search_text is '', app is None.

2013-04-18 11:56:50,782 - softwarecenter.db.pkginfo_impl.aptcache - INFO - aptcache.open()

Traceback (most recent call last):

  File "/usr/share/software-center/softwarecenter/db/pkginfo_impl/aptcache.py", line 243, in open

    self._cache = apt.Cache(GtkMainIterationProgress())

  File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 102, in __init__

    self.open(progress)

  File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 145, in open

    self._cache = apt_pkg.Cache(progress)

SystemError: E:Type 'ain' is not known on line 3 in source list /etc/apt/sources.list.d/sunab-kdenlive-release-precise.list, E:The list of sources could not be read., E:The package lists or status file could not be parsed or opened.

2013-04-18 11:56:54,320 - softwarecenter.db.enquire - ERROR - _get_estimate_nr_apps_and_nr_pkgs failed

Traceback (most recent call last):

  File "/usr/share/software-center/softwarecenter/db/enquire.py", line 115, in _get_estimate_nr_apps_and_nr_pkgs

    tmp_matches = enquire.get_mset(0, len(self.db), None, xfilter)

  File "/usr/share/software-center/softwarecenter/db/appfilter.py", line 89, in __call__

    if (not pkgname in self.cache and

  File "/usr/share/software-center/softwarecenter/db/pkginfo_impl/aptcache.py", line 263, in __contains__

    return self._cache.__contains__(k)

AttributeError: 'NoneType' object has no attribute '__contains__'

Traceback (most recent call last):

  File "/usr/bin/software-center", line 176, in 

    app.run(args)

  File "/usr/share/software-center/softwarecenter/ui/gtk3/app.py", line 1422, in run

    self.show_available_packages(args)

  File "/usr/share/software-center/softwarecenter/ui/gtk3/app.py", line 1352, in show_available_packages

    self.view_manager.set_active_view(ViewPages.AVAILABLE)

  File "/usr/share/software-center/softwarecenter/ui/gtk3/session/viewmanager.py", line 154, in set_active_view

    view_widget.init_view()

  File "/usr/share/software-center/softwarecenter/ui/gtk3/panes/availablepane.py", line 171, in init_view

    self.apps_filter)

  File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 238, in __init__

    self.build(desktopdir)

  File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 511, in build

    self._build_homepage_view()

  File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 271, in _build_homepage_view

    self._append_whats_new()

  File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 450, in _append_whats_new

    whats_new_cat = self._update_whats_new_content()

  File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 439, in _update_whats_new_content

    docs = whats_new_cat.get_documents(self.db)

  File "/usr/share/software-center/softwarecenter/db/categories.py", line 124, in get_documents

    nonblocking_load=False)

  File "/usr/share/software-center/softwarecenter/db/enquire.py", line 317, in set_query

    self._blocking_perform_search()

  File "/usr/share/software-center/softwarecenter/db/enquire.py", line 212, in _blocking_perform_search

    matches = enquire.get_mset(0, self.limit, None, xfilter)

  File "/usr/share/software-center/softwarecenter/db/appfilter.py", line 89, in __call__

    if (not pkgname in self.cache and

  File "/usr/share/software-center/softwarecenter/db/pkginfo_impl/aptcache.py", line 263, in __contains__

    return self._cache.__contains__(k)

AttributeError: 'NoneType' object has no attribute '__contains__'

I am using 12.04 64 bit