some problem about openstack compute nova

Hi,I installed Openstack Folsom on my PC with Ubuntu 12.04.But I always met some problems when I use the service nova.
For example,here is the nova list output :

root@ubuntu:/etc/init.d# nova list
ERROR:dbus.proxies:Introspect error on :1.22:/org/freedesktop/secrets/aliases/default: dbus.exceptions.DBusException: org.freedesktop.Secret.Error.NoSuchObject: The '/org/freedesktop/secrets/aliases/default' object does not exist
ERROR:dbus.connection:Unable to set arguments ({'org.freedesktop.Secret.Item.Label': 'http://10.108.195.149:5000/v2.0/admin//publicURL/compute// @ novaclient_auth', 'org.freedesktop.Secret.Item.Attributes': {'username': 'http://10.108.195.149:5000/v2.0/admin//publicURL/compute//', 'service': 'novaclient_auth'}}, dbus.Struct((dbus.ObjectPath('/org/freedesktop/secrets/session/s10'), '', dbus.ByteArray('fc8cfbdcc08344b0960109d5eb10b771|http://10.108.195.149:8774/v2/e53f362352fb496d8f6a6c36dfd8e941'), 'text/plain'), signature=None), True) according to signature None: <type 'exceptions.TypeError'>: Expected a string or unicode object
How can I deal with it ?Thanks.