Loading XHTML fragments over AJAX with jQuery

uncaught exception: Node cannot be inserted at the specified point in the hierarchy (NS_ERROR_DOM_HIERARCHY_REQUEST_ERR)
http://localhost:8000/static/1222832186/pixra/script/jquery-1.2.6.js
Line 257

$body = $("#div-to-fill");
$.get ("/testfile.xhtml", undefined, function (data)
{
    console.debug ("data = %o", data); // data = Document
    $body.children ().replaceWith (data); // error
}, 'xml');

<?xml version="1.0" encoding="UTF-8"?>
<div xmlns="http://www.w3.org/1999/xhtml">
  <form action="/gallery/image/edit-description/11529/" method="post">
    <div>content here</div>
  </form>
</div>

$body = $("#div-to-fill");
$.get ("/testfile.xhtml", function (data)
{
    $body.html($(data).children());
}, 'xml');