client side validation will show the error message in a javascript alert box.
since client side validation relies on java script, it i=will not function correctly if there are other javascript errors on the apge.
It looks like the line to define the progress bar on this page is missing, which is causing client validation to fail.
add the following code to the page in the head area:
<script src="webassist/progress_bar/jquery-blockui-formprocessing.js" type="text/javascript"></script>