node.save via XML-RPC generates error

On attempting node.save via XML-RPC service, error results and no node is created:

call_user_func_array() [<a href='function.call-user-func-array'>function.call-user-func-array</a>]: First argument is expected to be a valid callback, 'node_form' was given in /home/ixmati/drupal-6.3/includes/form.inc on line 359.

Environment is Drupal 6.3/Services 6.x-0.9/CCK 6.x-2.0. This error is generated when attempting to node.save either a core (page) or CCK content type.

The issue does not seem to involve node type caching issues, as I tried to ensure node types were reloaded as per this post:
http://source.mihelac.org/2008/4/22/drupal-forms-first-argument-is-expec...

XML-RPC post and response follow:

POST /services/xmlrpc HTTP/1.0
User-Agent: XML-RPC for PHP 2.2.1
Host: somehost.com:80
Accept-Charset: UTF-8,ISO-8859-1,US-ASCII
Content-Type: text/xml
Content-Length: 294

<?xml version="1.0"?>
<methodCall>
<methodName>node.save</methodName>
<params><param><value><struct><member><name>title</name><value><string>Page Test</string></value></member><member><name>type</name><value><string>page</string></value></member></struct></value></param></params>
</methodCall>
---END---

---GOT---
HTTP/1.1 200 OK
Date: Mon, 14 Jul 2008 19:08:10 GMT
Server: Apache/2.2.8 (Ubuntu) PHP/5.2.4-2ubuntu5.1 with Suhosin-Patch
X-Powered-By: PHP/5.2.4-2ubuntu5.1
Set-Cookie: somecookie; expires=Wed, 06 Aug 2008 22:41:30 GMT; path=/; domain=.somehost.com
Expires: Sun, 19 Nov 1978 05:00:00 GMT
Last-Modified: Mon, 14 Jul 2008 19:08:10 GMT
Cache-Control: store, no-cache, must-revalidate
Cache-Control: post-check=0, pre-check=0
Connection: close
Content-Length: 140
Content-Type: text/xml

<?xml version="1.0"?>

<methodResponse>
  <params>
  <param>
    <value><string></string></value>
  </param>
  </params>
</methodResponse>