Ajax Tabs not loading data

Ajax Tabs not loading data


I'm building a PHP site using tabs to re-query the database for
different criteria.
My problem is that even if the target ajax file contains <?php>echo
"testing";<?>, the tab just displays the "loading" message.
I noticed this also happens on the http://ui.jquery.com/demos/tabs#ajax
page but not when you click on the http://ui.jquery.com/applications/demos/tabs/ajax.html
link.
Any clues?