Comment 2 for bug 812923

Some additional debug info courtesy davmor2:

2011-07-20 18:55:09,515 - softwarecenter.backend.reviews - WARNING - Could not get usefulness from server, no username in config file
/home/davmor2/software-center/softwarecenter/ui/gtk/app.py:1240: Warning: g_object_set_qdata: assertion `G_IS_OBJECT (object)' failed
  self.window_main.show_all()
2011-07-20 18:55:10,081 - softwarecenter.fixme - WARNING - logs to the root logger: '('/usr/lib/pymodules/python2.7/zeitgeist/client.py', 392, 'reconnect_monitors')'
2011-07-20 18:55:10,081 - zeitgeist.client - INFO - Reconnected to Zeitgeist engine...
>>> histogram attr [0, 0, 1, 7, 7], for package tuxguitar
>>> histogram attr [2, 1, 3, 5, 49], for package docky
>>> histogram attr [0, 9, 3, 17, 40], for package calibre
>>> histogram attr [0, 1, 0, 9, 11], for package gweled
>>> histogram attr [1, 0, 0, 11, 16], for package file-roller
>>> histogram attr [0, 0, 1, 0, 0], for package netsurf
>>> histogram attr [0, 0, 0, 0, 5], for package mysql-server
>>> histogram attr [0, 0, 6, 15, 100], for package thunderbird
>>> histogram attr [0, 2, 4, 12, 54], for package deja-dup
>>> histogram attr [2, 0, 0, 0, 0], for package gfax
>>> histogram attr [0, 0, 2, 4, 9], for package kaffeine
>>> histogram attr None, for package python-django-south
Traceback (most recent call last):
  File "/home/davmor2/software-center/softwarecenter/backend/reviews.py", line 659, in _on_review_stats_data
    s.rating_spread = simplejson.loads(getattr(r, "histogram", "[0,0,0,0,0]"))
  File "/usr/lib/python2.7/dist-packages/simplejson/__init__.py", line 385, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python2.7/dist-packages/simplejson/decoder.py", line 402, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
TypeError: expected string or buffer