Hi, I've been using the form plugin to process some data in a form and was working perfectly until I added a new input (type="file") to upload images, for some reason now the plugin wont go past the beforeSubmit: section, the weird thing is that if I change the field type to text it works perfectly.

Is it something I'm doing wrong? Or do I have to do something else with file type fields? Here's the code, any help will be appreciated , thanks in advance!!

$('#add_form_mercancia').ajaxForm({
                    beforeSubmit: function (){   
                        if ($("#add_form_mercancia").valid()==false){
                            return false;
                        }

                        alert($("#add_form_mercancia").valid()); // <---- Outputs true
                },
                    success: function(r){

                        alert(r); // <----- Does nothing
                        if (r){
                            jAlert(r, 'Error');
                            $.fn.colorbox.close();
                        }else{
                            $('#table_div').load('mercancia.async.php?async=1','',tableSort);       //Actualizar tabla
                            $.fn.colorbox.close();   
                        }
                },
                    error: function(r){   
                        jAlert('Error procesando el formulario ->'+r,'Error');
                    }
 });