You need to disable simple membership:
<appSettings>
<add key="enableSimpleMembership" value="false"/>
</appSettings>
http://brockallen.com/2011/06/01/beware-bin-deployment-of-mvc-and-razor-with-formsauthentication/
Question
My custom routing have culture prefix and LoginPath in ConfigureAuth is changed accordingly. But after installing Microsoft.AspNet.WebHelpers package - and WebPages.WebData as dependency which is real source of problem, LoginPath setting is fully ignored and instead trying to go to /Account/Login which is wrong route. Is anybody knows workaround for this?
Solution
You need to disable simple membership:
<appSettings>
<add key="enableSimpleMembership" value="false"/>
</appSettings>
http://brockallen.com/2011/06/01/beware-bin-deployment-of-mvc-and-razor-with-formsauthentication/