I am completely new person on Linux. I installed it just today and i have to say I like them a lot, until I faced the problem. I was looking on the internet but nothing worked for me. After i downloaded skype and tried to run it, software center showed up and was loading something for 5 mins. then it just dessapeared. Now everytime I try to turn it on, the window is gone after 3 sec. I tried to kill it but didnt really wokrked. I get this message when trying to run it from the terminal:

 whats_new_cat = self._update_whats_new_content()
  File "/usr/share/software-center/softwarecenter/ui/gtk3/views/lobbyview.py", line 240, in _update_whats_new_content
    docs = whats_new_cat.get_documents(self.db)
  File "/usr/share/software-center/softwarecenter/db/categories.py", line 131, in get_documents
    nonblocking_load=False)
  File "/usr/share/software-center/softwarecenter/db/enquire.py", line 330, in set_query
    self._blocking_perform_search()
  File "/usr/share/software-center/softwarecenter/db/enquire.py", line 225, 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 281, in __contains__
    return self._cache.__contains__(k)
AttributeError: 'NoneType' object has no attribute '__contains

when trying to kill it via terminal, it says there is no process like this.

Thx guys for help! Help me like Ubuntu for rest of my life! :P