Hi
You have two references to the jQuery library in your page:
In line 16/17 you have a reference to the WA version:
<script type="text/javascript" src="webassist/jquery/jquery.js"></script> <script type="text/javascript" src="webassist/jquery/jquery-ui.js"></script>
In line 57 of your source code you have:
<script src="js/jquery-1.4.2.js" type="text/javascript"></script>
...which is causing the problem.
Try to comment that out and see, if it works.
HTH
Willi