This is not due to the 1.3 beta release - but could be due to the fact that you are linking to the latest version of JQuery. 1.20 supports JQuery 1.7.X - 1.8.2. JQuery latest is 1.9 which is definitely not supported/tested. You need to change it to link to 1.8.2.
Edit: Tested and confirmed. Use the 1.8.2 link similar to what you use for JQM.
<script src="http://code.jquery.com/jquery-1.8.2.min.js"></script>