FCK with jQuery ajaxForm plugin - old data sent to server

Hi there,
I'm attempting to use FCK in a form which is being handled by the jQuery ajaxForm plugin. The trouble is that if I make any changes in the editor, these are not sent in the POST to the server, the originial content is.
I have tried to manually update the original input element with the new data before the form is submitted using the beforeSubmit method provided by ajaxForm, but it doesn't work. The old data is still sent.
My ajaxForm snip looks like this:

    $(form_element + ' form').ajaxForm({
       target: form_element
       beforeSubmit: function(formArray, jqForm){
          // if any FCKEditors open, update their fields
          if (FCKeditorAPI)
          {
             for (i in FCKeditorAPI.Instances)
             {
                // TODO fix this, it doesn't work.
                FCKeditorAPI.Instances[i].UpdateLinkedField();
             }
             delete i;
          }
          
          return true;
       },
       success: function(data){
          // my success routine
       }
    });

Any ideas? I would rather not attempt to try and use tinyMCE again