Application execution problem

[Rich]

I am attempting to just demonstrate some basic mobile ASP.NET app
capabilities. I have created a new web application and inserted the
following demo code in the default.aspx page, which clearly does
nothing extraordinary:

<%@ Page language="c#"
Inherits="System.Web.UI.MobileControls.MobilePage" %>
<%@ Register TagPrefix="Mobile"
Namespace="System.Web.UI.MobileControls" Assembly="System.Web.Mobile"
%>
<mobile:Form id=Form1 runat="server">
<mobile:Label id=Test Runat="Server">Hello, Mobile World</
mobile:Label>
</mobile:Form>

I can build this site without problem but when I attempt to browse it
I get the following error:

Parser Error Message: The type
'System.Web.UI.MobileControls.MobilePage' is ambiguous: it could come
from assembly 'C:\WINDOWS\assembly\GAC_MSIL\System.Web.Mobile
\2.0.0.0__b03f5f7f11d50a3a\System.Web.Mobile.dll' or from assembly 'C:
\Documents and Settings\[username]\My Documents\Visual Studio
2005\Projects\mobile_demo\mobile_demo\bin\mobile_demo.DLL'. Please
specify the assembly explicitly in the type name.

Any ideas? I'm sure I'm doing something stupid but I can't figure it
out and 30 minutes of poking around the boards has yet to yield any
resolutions.

Thanks,
Rich