on your themed page, both the login form and the search form use a progress bar.
this is causing the jquery-blockui-formprocessing.js file to be included multiple times.
to prevent this i edited the login and top_products_search files. i changed:
<script src="../webassist/progress_bar/jquery-blockui-formprocessing.js" type="text/javascript"></script>
to:
<?php
if(!isset($progress) && $progress != "1") {
?>
<script src="../webassist/progress_bar/jquery-blockui-formprocessing.js" type="text/javascript"></script>
<?php
$progress = "1";
}
?>
I have also logged a bug that having that file on the page multiple times causes the form submit to fail