Troubleshooting Routing on localhost ASP.NET 3.5 SP1

Hello,

I would like to implement friendy URLs using routing. I started to test it in my dev environment with ASP.NET 3.5 and IIS 7.5 (Windows 7) running in Integrated mode.

I am following this article http://msdn.microsoft.com/en-us/library/cc668202(v=vs.90).aspx 

What I currently have is a product page with an URL like this

~/CatalogItem.aspx?id=100

and I would like to have the following URL

~/Items/100

I modified my application to match a VB code examples in the article above but when I access the catalog item page using the http://localhost/items/100 URL I get the following error

Line 21: 
Line 22:         strErrNote = "Getting user membership"
Line 23: If Membership.GetUser IsNot Nothing Then Line 24:             numUserId = Convert.ToInt16(Membership.GetUser.ProviderUserKey)
Line 25:             strUserId = numUserId.ToString

Source File: C:\WebSites\DobryCajCz_sub\App_Code\BasePage.vb    Line: 23 

on a page which I haven't modified for 2 years or so.

Public Class BasePage
    Inherits System.Web.UI.Page
 

Any suggestions how to troubleshoot it? Thanks!