Default Model Binder Does Not Bind Model Class

I am trying to make a post that should use the Default Model Binder functionality in ASP.NET MVC 2 but unfortunately I can't get through. When I click on the checkout button I populate a form dinamically using jQuery code and then submit this form to the server. This is the form that get submitted

<form action="/x/Order/Checkout" id="cartForm" method="post">
<input name="__RequestVerificationToken" type="hidden" value="UDjN9RdWheKyWK5Q71MvXAbbDNel6buJd5Pamp/jx39InuyYIQVptcEubIA2W8DMUzWwnZjSGkLspkmDPbsIxy8EVuLvfCSZJJnl/NrooreouptwM/PaBEz2v6ZjO3I26IKRGZPqLxGGfITYqlf8Ow==">
<input id="CustomerID" name="CustomerID" type="hidden" value="1">
<input id="FirmID" name="FirmID" type="hidden" value="2">
<input type="hidden" name="CartItems[0].ServiceTypeID" value="1">
<input type="hidden" name="CartItems[0].Quantity" value="1">
<input type="hidden" name="CartItems[1].ServiceTypeID" value="2">
<input type="hidden" name="CartItems[1].Quantity" value="1">
</form>

This is the jQuery code that handle the submit event for the form
$("#cartForm").submit(function (event) {
event.preventDefault(); var form = $("#cartForm");
var panel = form.parent(); panel.parent().block();
$.ajax({ type: "post", dataType: "html",
url: '<%: Url.Content("~/Order/Checkout") %>',
async: false, data: form.serialize(),
success: function (response, status, xml) { panel.parent().unblock(); },
error: function (response) { panel.parent().unblock(); } }); });

This is the controller action that should be get called
[HttpPost]
[ValidateAntiForgeryToken]
public virtual ActionResult Checkout( CartModel cart ) {
} And finally this is the CartModel class involved
public class CartModel : BaseModel{
public int CustomerID { get; set; }
public int FirmID { get; set; }
public List<CartItemModel> CartItems { get; set; }
public CartModel() { CartItems = new List<CartItemModel>();
} } public class CartItemModel : BaseModel
{ public int ServiceTypeID { get; set; }
public int Quantity { get; set; } }

But the default Model Binder does not bind the web form data to a CartModel class. Using Fiddler I have been able to see that the data sent to the server is correct as you can see from the following snapshot.