[jQuery] [validate]validate works for IE but Not for Firefox, Nor Opera Nor Safari Nor Chrome :S

[Bizzy]

Hey everybody,

I have been working on a project and i'm using the validation plugin
in one form, but something really strange is happening .. :S the
validation works perfectly on IE, but on firefox it just ignores it
and let you submit the fields empty even if they are required. can
anyone of you help me please?

Thanks in advance.

the code :

<script type="text/javascript" src="/js/jquery/validate/
jquery.ExtraValidation.js"></script>
<script type="text/javascript">
jQuery(document).ready(function(){
        jQuery("#frmEmployees").validate({
                rules: {
                                LastName:{ required: true }
                        },
                messages:{
                                LastName:{ required: "&nbsp;" },

                },
                success: function(label) {
                label.html("&nbsp;").addClass("checked");
                }
        })
});
</script>
        <!-- BEGIN UserInfoBlock -->
        <form name="frmEmployees" id="frmEmployees" method="post">
        <input type="hidden" name="ECAction" value="{{Action}}" />
        <input type="hidden" name="ECState" value="2" />
        <input type="hidden" name="UserID" value="{{UserID}}">
        <input type="hidden" name="EmployeeID" value="{{EmployeeID}}">
        <input type="hidden" name="AddID" value="{{AddID}}">
...
                                <tr>
                                        <td valign="middle">Test :</td>
                                        <td align="left"><input type="text" 
name="LastName"
id="LastName"></td>
                                </tr>
...
        <tr>
                <td align="right"><input type="submit" name="Submit" id="Submit"
value="Opslaan"></td>
        </tr>
        <tr>
                <td><br /><br /></td>
        </tr>
        </form>

Thanks!