The name 'XXXX' does not exists in current context

Hi...

In the Global.asax file I have something like this:
 
protected void Session_Start(object sender, EventArgs e)
  {
  System.Web.HttpContext.Current.Session["State"] = new Config.State();
 
  }

and this report me the error 'The name 'State' does not exists in current context'.
 
and I have class State in Config namespace:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Config
{
  public class State
  {
  public State()
  {
  //some code here
  }
  //some code here
  }
 
}

Any help oh this?