I\'m currently working on a Session expired piece of logic for my ASP.NET 3.5 MVC 2 project to log out a user and redirect them to the AccountController LogOn action.
ASP.NET will create a new session for every request unless you store something in it.
Try adding the code below to your Global.asax. It works in my MVC2 and MVC3 apps with the same SessionExpireFilterAttribute.