It appears that twitter has moved the tooltip script and it is not available for your site. If you can afford the traffic, you can serve it locally:
- Download twitter bootstrap.
- Extract
twbs-bootstrap-<somebuild>/js/bootstrap-tooltip.js
to some directory on your server (that is serverd, of course). - Change the line
<script src="http://twitter.github.com/bootstrap/assets/js/bootstrap-tooltip.js"></script>
to point to where you put the script.
This should probably solve your problem for the time being. You can search for a CDN that will provide a reliable URL for that file as a long-term solution.