Finally after a bunch of try and error, I figure it out
updated version of my script & it works for me
$(function(e) {
$('form#addProduct').submit(function(){
$(this).ajaxSubmit({
url:'add_product.php',
type:'post',
clearForm:'true',
resetForm:'true',
cache:'false',
success:function(msg){
$('div#confirm').slideDown("fast").html(msg).delay(2000).slideUp('slow');
$('div#add_sku').modal('hide');
$('div#showcase').load('show_product.php');
},
complete:function(){
$('form#addProduct').resetForm();
$('form#addProduct').clearForm();
},
error:function(err){
$('div#message').css('display','').html(err);
$('form#addProduct').resetForm();
$('form#addProduct').clearForm();
},
});
return false;
});