creation of 'empty nodes' instead of usernodes

i have a problem with usernode in combination with the 'advanced profile' and 'bio'-modules.

when i install usernode, every user that has been registered before the installation gets one usernode (as it should be), but everyone who registers afterwards gets no usernode, but an 'empty node' is created whenever he/she submits their account settings (not the bio/profile-info). these empty nodes have neither a title nor a content type assigned to them. they are all authored by Anonymous (uid=0). when i try to edit one of these node, i get the following error: warning: call_user_func_array(): First argumented is expected to be a valid callback, '_node_form' was given in [...]/html/includes/form.inc on line 218.
i tried with usernode stable (1.3), dev and the cvs-head. i tried simply de- and re-activating the module like often suggested here, but that doesn't work for me. i read that there are some problems related to mandatory cck-fields. my usernode doesn't have any fields, in my profile none is 'required'.

any idea how to deal with this is very appreciated.

sebastian