PubSub invalid configuration error

I am using the ruby xmpp4r library to try to create a PubSub node on ejabberd 2.0rc1.

The code tries to create a node called /pubsub/nodes/name, however ejabberd returns an error.

In the logs I can see:

=INFO REPORT==== 2008-02-03 22:58:11 ===
I(<0.293.0>:mod_pubsub:871) : Node "/pubsub/nodes/name" ; invalid configuration: []

The pubsub configuration is the default one, with everyone allowed to create nodes.

This is the request as sent from ejabberd:

=INFO REPORT==== 2008-02-03 22:24:42 ===
D(<0.339.0>:ejabberd_router:301) : route
from {jid,"username",
"localhost",
"3930206612120270282180863",
"username",
"localhost",
"3930206612120270282180863"}
to {jid,[],"localhost",[],[],"localhost",[]}
packet {xmlelement,
"iq",
[{"xml:lang","en"},
{"type","set"},
{"id","5924"},
{"to","localhost"}],
[{xmlelement,
"pubsub",
[{"xmlns","http://jabber.org/protocol/pubsub"}],
[{xmlelement,
"create",
[{"node","/pubsub/nodes/username/xx"}],
[]}]}]}

I tried different combinations of names but nothing worked.