HttpContext.Current.User changes Data Types

I am trying to get the HttpContext.Current.User to stick for my ADO.NET Data Service. 
By the time I try to use it, it has morphed into a GenericPrincipal object type.
The scenario is as such,
I have an ASP.NET website that I have incorporated my own custom Membership provider. 
I have an ADO.NET Data Service that is set as a startup page.  I run the app from within Visual Studio 2008.  The page is directed to the login page where I enter the login information.  The ValidateUser method does the validation and then sets the HttpContext.Current.User = principal and then I am returned to the Service site.  If I append an Entity on the URL address and check the HttpContext.Current.User it is a GenericPrincipal object.
I added Application_AuthenticateRequest to the Global.asax and found the same thing.
Any help is appreciated.
web.config
<syst ...