TypeError: can't compare datetime.date to int

[garmoncheg]

We are receiving this error once in a while on a tmsdemo host.

Traceback (most recent call last):

 File "/srv/www/tms/lib/python2.6/site-packages/django/core/handlers/base.py", line 111, in get_response
   response = callback(request, *callback_args, **callback_kwargs)

 File "/srv/www/tms/lib/python2.6/site-packages/django/contrib/auth/decorators.py", line 23, in _wrapped_view
   return view_func(request, *args, **kwargs)

 File "/srv/www/tms/src/adlibre_tms/apps/reporting/views.py", line 27, in reports_detail
   if request.method == "POST" and form.is_valid():

 File "/srv/www/tms/lib/python2.6/site-packages/django/forms/forms.py", line 121, in is_valid
   return self.is_bound and not bool(self.errors)

 File "/srv/www/tms/lib/python2.6/site-packages/django/forms/forms.py", line 112, in _get_errors
   self.full_clean()

 File "/srv/www/tms/lib/python2.6/site-packages/django/forms/forms.py", line 268, in full_clean
   self._clean_form()

 File "/srv/www/tms/lib/python2.6/site-packages/django/forms/forms.py", line 296, in _clean_form
   self.cleaned_data = self.clean()

 File "/srv/www/tms/src/adlibre_tms/apps/tms/forms.py", line 156, in clean
   if date_start > date_end:

TypeError: can't compare datetime.date to int

with full paste here:
http://dpaste.com/827897/