Every tab in the stats section shows this error:

Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/prewikka/Core.py", line 350, in process
    getattr(view_object, view["handler"])()
  File "/usr/lib/python2.6/site-packages/prewikka/views/stats.py", line 504, in render
    self._renderClassificationsTrend(criteria)
  File "/usr/lib/python2.6/site-packages/prewikka/views/stats.py", line 493, in _renderClassificationsTrend
    "alert.classification.text", criteria, limit = 10, zoom_type="classifications_trend")
  File "/usr/lib/python2.6/site-packages/prewikka/views/stats.py", line 448, in _addTimelineChart
    timeline.render(title)
  File "/usr/lib/python2.6/site-packages/prewikka/Chart.py", line 311, in render
    x_labels = self._labels, series_legend=True, series_colors=colors)
  File "/usr/lib/python2.6/site-packages/prewikka/cairoplot.py", line 2003, in dot_line_plot
    plot.render()
  File "/usr/lib/python2.6/site-packages/prewikka/cairoplot.py", line 451, in render
    self.calc_all_extents()
  File "/usr/lib/python2.6/site-packages/prewikka/cairoplot.py", line 416, in calc_all_extents
    self.calc_extents(HORZ)
  File "/usr/lib/python2.6/site-packages/prewikka/cairoplot.py", line 393, in calc_extents
    self.max_value[direction] = max(self.context.text_extents(item)[2] for item in self.labels[direction])
  File "/usr/lib/python2.6/site-packages/prewikka/cairoplot.py", line 393, in <genexpr>
    self.max_value[direction] = max(self.context.text_extents(item)[2] for item in self.labels[direction])
MemoryError