admin extension list instances fails with KeyError

When trying to access the Instances tab in the System panel in Horizon, returns this error message every time:

Error: Unable to get instance list: The server has either erred or is incapable of performing the requested operation.

In the nova-api log file, you can see the root cause of the problem:

2011-12-03 16:30:46,864 DEBUG nova.api.openstack.common [-] Generated ACTIVE from vm_state=active task_state=None. from (pid=3976) status_from_state /opt/stack/nova/nova/api/openstack/common.py:92
2011-12-03 16:30:46,864 DEBUG nova.api.openstack.common [-] Generated ACTIVE from vm_state=active task_state=None. from (pid=3976) status_from_state /opt/stack/nova/nova/api/openstack/common.py:92
2011-12-03 16:30:46,864 DEBUG nova.api.openstack.common [-] Generated ACTIVE from vm_state=active task_state=None. from (pid=3976) status_from_state /opt/stack/nova/nova/api/openstack/common.py:92
2011-12-03 16:30:46,867 ERROR nova.api.openstack.v2 [-] Caught error: '4d46fcff-5b5e-4ca3-baa3-fe4ab54e1ee7'
(nova.api.openstack.v2): TRACE: Traceback (most recent call last):
(nova.api.openstack.v2): TRACE: File "/opt/stack/nova/nova/api/openstack/v2/__init__.py", line 61, in __call__
(nova.api.openstack.v2): TRACE: return req.get_response(self.application)
(nova.api.openstack.v2): TRACE: File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1053, in get_response
(nova.api.openstack.v2): TRACE: application, catch_exc_info=False)
(nova.api.openstack.v2): TRACE: File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1022, in call_application
(nova.api.openstack.v2): TRACE: app_iter = application(self.environ, start_response)
(nova.api.openstack.v2): TRACE: File "/opt/stack/keystone/keystone/middleware/auth_token.py", line 212, in __call__
(nova.api.openstack.v2): TRACE: return self._forward_request(env, start_response, proxy_headers)
(nova.api.openstack.v2): TRACE: File "/opt/stack/keystone/keystone/middleware/auth_token.py", line 344, in _forward_request
(nova.api.openstack.v2): TRACE: return self.app(env, start_response)
(nova.api.openstack.v2): TRACE: File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 159, in __call__
(nova.api.openstack.v2): TRACE: return resp(environ, start_response)
(nova.api.openstack.v2): TRACE: File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 147, in __call__
(nova.api.openstack.v2): TRACE: resp = self.call_func(req, *args, **self.kwargs)
(nova.api.openstack.v2): TRACE: File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 208, in call_func
(nova.api.openstack.v2): TRACE: return self.func(req, *args, **kwargs)
(nova.api.openstack.v2): TRACE: File "/opt/stack/nova/nova/api/openstack/wsgi.py", line 499, in __call__
(nova.api.openstack.v2): TRACE: response = req.get_response(self.application)
(nova.api.openstack.v2): TRACE: File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1053, in get_response
(nova.api.openstack.v2): TRACE: application, catch_exc_info=False)
(nova.api.openstack.v2): TRACE: File "/usr/lib/python2.7/dist-packages/webob/request.py", line 1022, in call_application
(nova.api.openstack.v2): TRACE: app_iter = application(self.environ, start_response)
(nova.api.openstack.v2): TRACE: File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 159, in __call__
(nova.api.openstack.v2): TRACE: return resp(environ, start_response)
(nova.api.openstack.v2): TRACE: File "/usr/lib/pymodules/python2.7/routes/middleware.py", line 131, in __call__
(nova.api.openstack.v2): TRACE: response = self.app(environ, start_response)
(nova.api.openstack.v2): TRACE: File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 159, in __call__
(nova.api.openstack.v2): TRACE: return resp(environ, start_response)
(nova.api.openstack.v2): TRACE: File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 147, in __call__
(nova.api.openstack.v2): TRACE: resp = self.call_func(req, *args, **self.kwargs)
(nova.api.openstack.v2): TRACE: File "/usr/lib/python2.7/dist-packages/webob/dec.py", line 208, in call_func
(nova.api.openstack.v2): TRACE: return self.func(req, *args, **kwargs)
(nova.api.openstack.v2): TRACE: File "/opt/stack/nova/nova/api/openstack/wsgi.py", line 567, in __call__
(nova.api.openstack.v2): TRACE: action_result = self.dispatch(request, action, args)
(nova.api.openstack.v2): TRACE: File "/opt/stack/nova/nova/api/openstack/wsgi.py", line 599, in dispatch
(nova.api.openstack.v2): TRACE: return controller_method(req=request, **action_args)
(nova.api.openstack.v2): TRACE: File "/opt/stack/openstackx/extensions/admin.py", line 223, in index
(nova.api.openstack.v2): TRACE: s['attrs'] = self._build_extended_attributes(instance_map[s['id']])
(nova.api.openstack.v2): TRACE: KeyError: '4d46fcff-5b5e-4ca3-baa3-fe4ab54e1ee7'

I believe the openstackx admin extension may need to be updated to use the UUID and not the ID?