ViewSwitcher posting back to currently loaded url

This one has been driving me nuts for weeks.
If I navigate to the site with a mobile the mobile page loads but refuses to change to the desktop view when clicked (the url is actually mobile.pagename).  
Mobile url = http://localhost:57387/Default.Mobile
Click 'Switch to Desktop' http://localhost:57387/Default.Mobile?ReturnUrl=%2fDefault.Mobile
Click the link again http://localhost:57387/Default.Mobile?ReturnUrl=%2fDefault.Mobile%3fReturnUrl%3d%252fDefault.Mobile

Any ideas?
Thanks
ViewSwitcher.ascx.vb
Imports Microsoft.AspNet.FriendlyUrls.Resolvers Public Class ViewSwitcher Inherits System.Web.UI.UserControl Protect ...