We have an internal ASP.NET Webforms application running on a Windows 2008/IIS7 server which has been running fine until we installed MVC3.
Now any requests redirect to /Account/Login?ReturnUrl=%2f.
The website is Webforms not MVC. Because it is an internal only site we have Windows Authentication enabled for the root folder.
We have several other websites on the same server that have not been affected by this problem, but this is the only site where the root folder is set to Windows Authentication.
I solved the problem by adding the following lines to the AppSettings section of my web.config file:
<add key="autoFormsAuthentication" value="false" /> <add key="enableSimpleMembership" value="false"/>