mozilla firefox in 3-5 menit hang or (macet)

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Error Type: <type 'exceptions.TypeError'>
Error Value: coercing to Unicode: need string or buffer, exceptions.SystemError found
  File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 2216, in <module>
    main()
  File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 2213, in main
    run(args, options.single)
  File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 2175, in run
    backend.dispatcher(args)
  File : /usr/lib/python2.6/dist-packages/packagekit/backend.py, line 699, in dispatcher
    self.dispatch_command(args[0], args[1:])
  File : /usr/lib/python2.6/dist-packages/packagekit/backend.py, line 606, in dispatch_command
    self.refresh_cache(force)
  File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 202, in _locked_cache
    func(*args, **kwargs)
  File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 1498, in refresh_cache
    format_string(error.message))
  File : /usr/lib/python2.6/dist-packages/packagekit/backend.py, line 723, in format_string
    txt = unicode(text, encoding, errors='replace')