I have set tow nodes: precise64 and slave101, and both of them seems to work properly.

vagrant@precise64:~$ nova-manage service list
Binary           Host                                 Zone             Status     State Updated_At
nova-network     slave101                             nova             enabled    :-)   2013-01-08 05:28:24
nova-compute     slave101                             nova             enabled    :-)   2013-01-08 05:28:24
nova-conductor   precise64                            nova             enabled    :-)   2013-01-08 05:28:22
nova-cert        precise64                            nova             enabled    :-)   2013-01-08 05:28:24
nova-compute     precise64                            nova             enabled    :-)   2013-01-08 05:28:24
nova-network     precise64                            nova             enabled    :-)   2013-01-08 05:28:26
nova-scheduler   precise64                            nova             enabled    :-)   2013-01-08 05:28:26
nova-consoleauth precise64                            nova             enabled    :-)   2013-01-08 05:28:24

when i try to create an instance with "nova boot",the error happens:
vagrant@precise64:~$ nova boot --hint force_hosts=slave101 --flavor 1 --image a566bbb7-ef41-4fea-8f60-157d86873b22 image01

2013-01-08 05:29:17 DEBUG nova.scheduler.filter_scheduler [req-dff32077-fe8c-49d9-8784-25be8f692d8a admin demo] Attempting to build 1 instance(s) from (pid=9080) schedule_run_instance /opt/stack/nova/nova/scheduler/filter_scheduler.py:53
2013-01-08 05:29:17 WARNING nova.scheduler.manager [req-dff32077-fe8c-49d9-8784-25be8f692d8a admin demo] Failed to schedule_run_instance: can't compare datetime.datetime to NoneType
2013-01-08 05:29:17 WARNING nova.scheduler.manager [req-dff32077-fe8c-49d9-8784-25be8f692d8a admin demo] [instance: 631f69ff-9827-427f-a5d0-e59359687519] Setting instance to ERROR state.
2013-01-08 05:29:17 ERROR nova.openstack.common.rpc.amqp [req-dff32077-fe8c-49d9-8784-25be8f692d8a admin demo] Exception during message handling
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp Traceback (most recent call last):
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp   File "/opt/stack/nova/nova/openstack/common/rpc/amqp.py", line 277, in _process_data
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp     rval = self.proxy.dispatch(ctxt, version, method, **args)
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp   File "/opt/stack/nova/nova/openstack/common/rpc/dispatcher.py", line 147, in dispatch
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp     return getattr(proxyobj, method)(ctxt, **kwargs)
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp   File "/opt/stack/nova/nova/scheduler/manager.py", line 121, in run_instance
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp     context, ex, request_spec)
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp   File "/usr/lib/python2.7/contextlib.py", line 24, in __exit__
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp     self.gen.next()
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp   File "/opt/stack/nova/nova/scheduler/manager.py", line 109, in run_instance
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp     requested_networks, is_first_time, filter_properties)
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp   File "/opt/stack/nova/nova/scheduler/filter_scheduler.py", line 60, in schedule_run_instance
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp     filter_properties, instance_uuids)
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp   File "/opt/stack/nova/nova/scheduler/filter_scheduler.py", line 256, in _schedule
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp     hosts = self.host_manager.get_all_host_states(elevated)
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp   File "/opt/stack/nova/nova/scheduler/host_manager.py", line 388, in get_all_host_states
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp     host_state.update_from_compute_node(compute)
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp   File "/opt/stack/nova/nova/scheduler/host_manager.py", line 143, in update_from_compute_node
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp     if self.updated and self.updated > compute['updated_at']:
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp TypeError: can't compare datetime.datetime to NoneType
2013-01-08 05:29:17 TRACE nova.openstack.common.rpc.amqp

anyone can help me?  thank you