[jQuery] (validate) Problems with additional methods...

Hello everybody!

I'm trying to use a custom method for validate one of my input's form,
but no way.

Neither the 'additional-methods.js' included in the plugin pack work
for me ....Seems to be ok,  but no idea.

This is a resume of my code:

-JAVASCRIPT-

<script type="text/javascript">
$.validator.setDefaults({
        submitHandler: function() {
                $("#cForm").ajaxSubmit({
                        url:'inc/request.php',
                        target: '#form-box',
                        success: function(){
                                return false;
                        },
                        resetForm: true
                });
        }
});

$(document).ready(function(){
        $("#cForm").validate({
                rules:{
                        nif: "alphanumeric",
                },
                messages: {
                        nombre: "campo obligatorio",
                        email: {
                                required: "campo obligatorio",
                                email: "email no valido"
                        },
                        telefono: {
                                required: "campo obligatorio",
                                digits: "solo numeros"
                        },
                        nif: "campo obligatorio",
                        legal: "campo obligatorio"
                },
                errorElement: "em",
                errorPlacement: function(error, element) {
                        if ( element.is(":radio") )
                                error.appendTo(element.parent().parent());
                        else if ( element.is(":checkbox") )
                                error.appendTo(element.parent());
                        else
                                error.prependTo( element.parent() );
                }
        });
});
</script>

-HTML-
...

<form action="" method="post" id="cForm">
                <div>
                    <label for="nombre">Nombre y Apellidos</label>
                    <input class="required" type="text" size="25"
name="nombre" id="nombre" value="" maxlength="100"/>
                </div>
                <div>
                    <label for="nif">NIF</label>
                    <input class="required" type="text" size="9"
name="nif" id="nif" value="" maxlength="9"/>
                </div>
                <div>
                    <label for="telefono">Teléfono</label>
                    <input class="required digits" type="text"
size="10" name="telefono" id="telefono" value="" maxlength="15"/>
                </div>
                <div>
                    <label for="email">E-mail</label>
                    <input class="required email" type="text"
size="25" name="email" id="email" value="" maxlength="100"/>
                </div>
                <div class="row">
                    <input class="required" name="legal" id="legal"
type="checkbox"/>
                    <label for="legal">He leído y acepto las bases
legales</a></label>
                    <input type="submit" name="submit" id="send"
value="" />
                </div>
</form>
...


Thanks in advance!

Best Regards,

Andrea