FormsAuthentication.SignOut() not working.

Here is the flow of the test I just ran: I start my web page, attempt to access a page w/o loggin in, I am redirected to log in.  So far so good.  I log in to the system and go to my default page.  I now try to access an administrator resource as a non-administrator user, so I am redirected to the login page, the login page realizes I am already authenticated and forwards me to the default page (thus avoiding the "confusing workflow" situation presented in the tutorial).  Again, so far so good.
Now is when trouble happens.  On the default page I click Logout, and I am forwarded to the logout page.  The logout page has the following code behind it:
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web ...