I'm having a similar issue with the ec2 commands, although my traceback is very different:
(root): 2012-03-18 22:20:28,196 DEBUG utils _calc_signature_2 base64 encoded digest: 5hkz+Ok1N4fy/6lBMvYu0e4A/Li3AYeGC07F3oj9RH8=
(eventlet.wsgi.server): 2012-03-18 22:20:28,199 DEBUG wsgi write Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/eventlet/wsgi.py", line 336, in handle_one_response
    result = self.application(self.environ, start_response)
  File "/usr/lib/python2.7/dist-packages/paste/urlmap.py", line 203, in __call__
    return app(environ, start_response)
  File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 147, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 210, in call_func
    return self.func(req, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/keystone/common/wsgi.py", line 293, in __call__
    response = request.get_response(self.application)
  File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1086, in get_response
    application, catch_exc_info=False)
  File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1055, in call_application
    app_iter = application(self.environ, start_response)
  File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 147, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 210, in call_func
    return self.func(req, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/keystone/common/wsgi.py", line 293, in __call__
    response = request.get_response(self.application)
  File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1086, in get_response
    application, catch_exc_info=False)
  File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1055, in call_application
    app_iter = application(self.environ, start_response)
  File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 147, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 210, in call_func
    return self.func(req, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/keystone/common/wsgi.py", line 293, in __call__
    response = request.get_response(self.application)
  File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1086, in get_response
    application, catch_exc_info=False)
  File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1055, in call_application
    app_iter = application(self.environ, start_response)
  File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 147, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 210, in call_func
    return self.func(req, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/keystone/common/wsgi.py", line 293, in __call__
    response = request.get_response(self.application)
  File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1086, in get_response
    application, catch_exc_info=False)
  File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1055, in call_application
    app_iter = application(self.environ, start_response)
  File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 147, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 210, in call_func
    return self.func(req, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/keystone/common/wsgi.py", line 316, in __call__
    resp = req.get_response(self.application)
  File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1086, in get_response
    application, catch_exc_info=False)
  File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1055, in call_application
    app_iter = application(self.environ, start_response)
  File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 159, in __call__
    return resp(environ, start_response)
  File "/usr/lib/python2.7/dist-packages/routes/middleware.py", line 131, in __call__
    response = self.app(environ, start_response)
  File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 159, in __call__
    return resp(environ, start_response)
  File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 147, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 210, in call_func
    return self.func(req, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/keystone/common/wsgi.py", line 181, in __call__
    result = method(context, **params)
  File "/usr/lib/python2.7/dist-packages/keystone/contrib/ec2/core.py", line 171, in authenticate
    user_id=user_ref['id'],
TypeError: 'NoneType' object has no attribute '__getitem__'


(eventlet.wsgi.server): 2012-03-18 22:20:28,216 DEBUG wsgi write 192.168.122.168 - - [18/Mar/2012 22:20:28] "POST /v2.0/ec2tokens HTTP/1.1" 500 4733 0.029336