hmmm... interesting... it should be loading jquery form... but a quick search and I see it only being loaded in the admin... but, seems like that would break it always...
worth a quick check... can you go to sp-forum-framework.php, function sp_load_forum_scripts() and at the bottom of the loading the other jquery stuff, can you add
wp_enqueue_script('jquery.form', SFWPJSCRIPT.'jquery.form.js', array('jquery'), false, $footer);
and see if that helps... obviously not a final implementation, but should get it loaded...