Deploying Asp.Net MVC 2 /C# 4.0 application on IIS 6

I think I know what's happening: on IIS6, as well as the wildcard mapping you will need a default document (Default.aspx) that routes folder requests to the MVC handler.

There was one included with the MVC1 project templates, but it has been removed in MVC2.

Default.aspx:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="YourNameSpace._Default" %>

<%-- Please do not delete this file. It is used to ensure that ASP.NET MVC is activated by IIS when a user makes a "/" request to the server. --%>

and Default.aspx.cs:

using System.Web;
using System.Web.Mvc;
using System.Web.UI;

namespace YourNameSpace
{
    public partial class _Default : Page
    {
        public void Page_Load(object sender, System.EventArgs e)
        {
            // Change the current path so that the Routing handler can correctly interpret
            // the request, then restore the original path so that the OutputCache module
            // can correctly process the response (if caching is enabled).

            string originalPath = Request.Path;
            HttpContext.Current.RewritePath(Request.ApplicationPath, false);
            IHttpHandler httpHandler = new MvcHttpHandler();
            httpHandler.ProcessRequest(HttpContext.Current);
            HttpContext.Current.RewritePath(originalPath, false);
        }
    }
}

When you say "It's as if the routing was not taken into account", I suspect that it actually isn't, and this is your problem.