12.04 - Ubuntu software center crashes on startup

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

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.

This is the cause of your problem it would seem. Perhaps if you don't want this PPA to remain, you should sudo rm /etc/apt/sources.list.d/sunab-kdenlive-release-precise.list to delete the file, then run sudo apt-get update to update the sources, then try to open Software Center again.

Aside from that, the crash itself is a bug, and you should file a bug report about it, as bug reports are off topic for Ask Ubuntu.