When I use the VMwareVCDriver, the system report Error as follows. Any one has any idea?

2013-09-07 21:03:10.556 31017 CRITICAL nova.virt.vmwareapi.driver [-] In vmwareapi:_call_method, got this exception: Server raised fault: ''
2013-09-07 21:03:10.556 31017 ERROR nova.all [-] Failed to load nova-compute
2013-09-07 21:03:10.556 31017 TRACE nova.all Traceback (most recent call last):
2013-09-07 21:03:10.556 31017 TRACE nova.all   File "/usr/local/lib/python2.7/dist-packages/nova/cmd/all.py", line 88, in main
2013-09-07 21:03:10.556 31017 TRACE nova.all     manager=manager))
2013-09-07 21:03:10.556 31017 TRACE nova.all   File "/usr/local/lib/python2.7/dist-packages/nova/service.py", line 257, in create
2013-09-07 21:03:10.556 31017 TRACE nova.all     db_allowed=db_allowed)
2013-09-07 21:03:10.556 31017 TRACE nova.all   File "/usr/local/lib/python2.7/dist-packages/nova/service.py", line 139, in __init__
2013-09-07 21:03:10.556 31017 TRACE nova.all     self.manager = manager_class(host=self.host, *args, **kwargs)
2013-09-07 21:03:10.556 31017 TRACE nova.all   File "/usr/local/lib/python2.7/dist-packages/nova/compute/manager.py", line 406, in __init__
2013-09-07 21:03:10.556 31017 TRACE nova.all     self.driver = driver.load_compute_driver(self.virtapi, compute_driver)
2013-09-07 21:03:10.556 31017 TRACE nova.all   File "/usr/local/lib/python2.7/dist-packages/nova/virt/driver.py", line 1049, in load_compute_driver
2013-09-07 21:03:10.556 31017 TRACE nova.all     virtapi)
2013-09-07 21:03:10.556 31017 TRACE nova.all   File "/usr/local/lib/python2.7/dist-packages/nova/openstack/common/importutils.py", line 52, in import_object_ns
2013-09-07 21:03:10.556 31017 TRACE nova.all     return import_class(import_value)(*args, **kwargs)
2013-09-07 21:03:10.556 31017 TRACE nova.all   File "/usr/local/lib/python2.7/dist-packages/nova/virt/vmwareapi/driver.py", line 409, in __init__
2013-09-07 21:03:10.556 31017 TRACE nova.all     self._session, self._cluster_name)
2013-09-07 21:03:10.556 31017 TRACE nova.all   File "/usr/local/lib/python2.7/dist-packages/nova/virt/vmwareapi/vm_util.py", line 691, in get_cluster_ref_from_name
2013-09-07 21:03:10.556 31017 TRACE nova.all     "ClusterComputeResource", ["name"])
2013-09-07 21:03:10.556 31017 TRACE nova.all   File "/usr/local/lib/python2.7/dist-packages/nova/virt/vmwareapi/driver.py", line 573, in _call_method
2013-09-07 21:03:10.556 31017 TRACE nova.all     return temp_module(*args, **kwargs)
2013-09-07 21:03:10.556 31017 TRACE nova.all   File "/usr/local/lib/python2.7/dist-packages/nova/virt/vmwareapi/vim_util.py", line 200, in get_objects
2013-09-07 21:03:10.556 31017 TRACE nova.all     specSet=[property_filter_spec], options=options)
2013-09-07 21:03:10.556 31017 TRACE nova.all   File "/usr/local/lib/python2.7/dist-packages/nova/virt/vmwareapi/vim.py", line 172, in vim_request_handler
2013-09-07 21:03:10.556 31017 TRACE nova.all     raise error_util.VimFaultException(fault_list, excep)
2013-09-07 21:03:10.556 31017 TRACE nova.all VimFaultException: Server raised fault: ''