Django error from session/ TypeError: expected string or buffer

[ksnabb]

Traceback (most recent call last):

File "/l/apps/softgis/geonition20.env/lib/python2.6/site-packages/Django-1.4-py2.6.egg/django/core/handlers/base.py", line 111, in get_response
response = callback(request, _callback_args, *_callback_kwargs)

File "/l/apps/softgis/geonition20.env/lib/python2.6/site-packages/gntauth-4.0.1-py2.6.egg/gntauth/views.py", line 243, in session
return HttpResponse(request.session.session_key)

File "build/bdist.linux-x86_64/egg/geonition_utils/http.py", line 13, in init
message_to_json(message),

File "build/bdist.linux-x86_64/egg/geonition_utils/http.py", line 104, in message_to_json
message_dict = json.loads(message)

File "/usr/lib64/python2.6/site-packages/simplejson/init.py", line 307, in loads
return _default_decoder.decode(s)

File "/usr/lib64/python2.6/site-packages/simplejson/decoder.py", line 335, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())

TypeError: expected string or buffer

This error needs to be looked into