test_timeline_graph Windmill test is failing

The test_timeline_graph Windmill test is failing is consistently failing in the jscheck buildbot builder:

(from https://lpbuildbot.canonical.com/builders/jscheck/builds/227/steps/shell_7/logs/summary)

Failure in test lp.registry.windmill.tests.test_timeline_graph.TestTimelineGraph.test_timeline_graph
Traceback (most recent call last):
  File "/srv/buildbot/slaves/launchpad/jscheck/build/lib/lp/testing/__init__.py", line 450, in run
    testMethod()
  File "/srv/buildbot/slaves/launchpad/jscheck/build/lib/lp/registry/windmill/tests/test_timeline_graph.py", line 27, in test_timeline_graph
    timeout=u'8000')
  File "/srv/buildbot/slaves/launchpad/jscheck/build/orig_sourcecode/eggs/windmill-1.3beta3_lp_r1440-py2.5.egg/windmill/authoring/__init__.py", line 161, in __call__
    return self.exec_method(self.action_name, **kwargs)
  File "/srv/buildbot/slaves/launchpad/jscheck/build/orig_sourcecode/eggs/windmill-1.3beta3_lp_r1440-py2.5.egg/windmill/authoring/__init__.py", line 214, in _exec_test
    raise WindmillTestClientException(result['result'])
WindmillTestClientException: {'suite_name': 'TimelineGraph', 'result': False, 'starttime': '2009-11-8T17:54:7.589Z', 'params': {'id': 'spinner', 'timeout': '8000', 'option': 'style.display|none'}, 'output': None, 'endtime': '2009-11-8T17:54:15.705Z', 'method': 'waits.forElementProperty'}