URL Rewriting And 301 Redirect... Redirects To The Original URL

In answering another persons question here on SO, I discovered that there is a small "bug" in my global redirect code.I have wired up a Global class to an HttpModule. It's job is to detect "http:/www." in the URL and redirect the user to the NON www. version

Protected Sub OnBeginRequest(ByVal sender As Object, ByVal e As EventArgs)
'Force Removal of WWW
Dim application As HttpApplication = TryCast(sender, HttpApplication)
[code]....

when it redirect a page http://www.example.com/AboutUs, the goal is to have it go to http://example.com/AboutUs (the rewritten page) but instead it's going to http://example.com/Default.aspx?Slug=AboutUs (the original page).I tried doing a bit of a hack by changing

Dim newUrl As [String] = UrlRegex.Replace(url.ToString(), [String].Format("{0}://", url.Scheme))
application.Context.Response.Status = "301 Moved Permanently"
application.Context.Response.AddHeader("Location", newUrl.Replace("Default.aspx", ""))
to

Dim newUrl As [String] = UrlRegex.Replace(url.ToString(), [String].Format("{0}://", url.Scheme))
newUrl = newUrl.Replace("Default.aspx?Slug=", "")
newUrl = newUrl.Replace("Default.aspx", "")
application.Context.Response.Status = "301 Moved Permanently"
application.Context.Response.AddHeader("Location", newUrl)

not something I want to do anyways since it's a hack, but it didn't work anyways.