jquery navigation code does not work properly

jquery navigation code does not work properly

I have written a complete website. I have used my own jquery navigation
plugin in it. It works in my localhost, but the hosted version fails to do
so. The problem is reported by the firebug is: mtNav() is not a function.
I don't know what to do. Because the source script of nav plugin is loaded
completely. Here is the URL to the site:
http://www.ms-models.com
Just the third item in the top-navigation should include drop-down menus.
Please ignore the language, just check the third item of nav menu.
Here is the loaded script:
http://ms-models.com/js/jquery.js
and here is the plugin applied to the navigation bar.
<script type="text/javascript">
$(document).ready(function(e) {
$('.top-navigation ul').mtNav();
});
</script>
Thanks in advance