Error when trying to import my State Senate District 16-only district index file.

celeryd-ohio-excerpt.log

[2011-07-08 16:54:00,264: ERROR/MainProcess] Task redistricting.utils.index2plan[053e21e9-7bad-4693-b96a-73e
88872da5d] raised exception: GEOSException('Error encountered checking Geometry returned from GEOS C functio
n "GEOSDifference_r".',)
Traceback (most recent call last):
  File "/usr/local/lib/python2.6/dist-packages/celery-2.1.4-py2.6.egg/celery/execute/trace.py", line 34, in 
trace
    return cls(states.SUCCESS, retval=fun(*args, **kwargs))
  File "/usr/local/lib/python2.6/dist-packages/celery-2.1.4-py2.6.egg/celery/task/base.py", line 248, in __c
all__
    return self.run(*args, **kwargs)
  File "/usr/local/lib/python2.6/dist-packages/celery-2.1.4-py2.6.egg/celery/decorators.py", line 52, in run
    return fun(*args, **kwargs)
  File "/projects/publicmapping_ohiov1.2/trunk/django/publicmapping/redistricting/utils.py", line 321, in index2plan
    create_unassigned_district(plan, instance=plan, created=True)
  File "/projects/publicmapping_ohiov1.2/trunk/django/publicmapping/redistricting/models.py", line 2533, in create_unassigned_district
    geounits = Geounit.get_mixed_geounits(geounit_ids, plan.legislative_body, biggest_geolevel.id, unassigned.geom, True)
  File "/projects/publicmapping_ohiov1.2/trunk/django/publicmapping/redistricting/models.py", line 461, in get_mixed_geounits
    intersects = selection.difference(union)
  File "/usr/local/lib/python2.6/dist-packages/Django-1.2.3-py2.6.egg/django/contrib/gis/geos/geometry.py", line 552, in difference
    return self._topology(capi.geos_difference(self.ptr, other.ptr))
  File "/usr/local/lib/python2.6/dist-packages/Django-1.2.3-py2.6.egg/django/contrib/gis/geos/prototypes/threadsafe.py", line 53, in __call__
    return call_geos_threaded(self.cfunc, args)
  File "/usr/local/lib/python2.6/dist-packages/Django-1.2.3-py2.6.egg/django/contrib/gis/geos/prototypes/threadsafe.py", line 33, in call_geos_threaded
    return cfunc(thread_context.handle.ptr, *args)
  File "/usr/local/lib/python2.6/dist-packages/Django-1.2.3-py2.6.egg/django/contrib/gis/geos/prototypes/errcheck.py", line 43, in check_geom
    raise GEOSException('Error encountered checking Geometry returned from GEOS C function "%s".' % func.__name__)
GEOSException: Error encountered checking Geometry returned from GEOS C function "GEOSDifference_r".