your page has multiple instances of jquery being used:
<script type="text/javascript" src="../ScriptLibrary/jquery-latest.pack.js"></script>
<script type="text/javascript" src="../ScriptLibrary/jquery.easing.1.3.js"></script>
<script type="text/javascript" src="../webassist/jquery/jquery.js"></script>
<script type="text/javascript" src="../webassist/jquery/jquery-ui.js"></script>
these 2 jquery libraries are causing a conflict and causing the datepicker to fail.