pageLinkedFrommust be the URL to a permalink archive page on my blog (complete with #fragment) and pageLinkedTomust be the URL of a page that contains a link to pageLinkedFrom.  My server is a bit flaky at the moment (hosting problems again) so you may need to repeat the ping a few times before it gets accepted.  Stuart’s PingBack server can be found at http://www.kryogenix.org/mt/mt-xmlrpc.cgi.  Both of our blogs now include a link element pointing to our PingBack servers, with the rel attribute set to “pingback” and the href attribute indicating the server URL.  The link elements should enable auto-discovery of PingBack servers in the future (an idea based on Mark Pilgrim’s RSS auto-discovery).