When areas are introduced, there is the potential for ambiguity between identically named Controllers ref: http://haacked.com/archive/2010/01/12/ambiguous-controller-names.aspx
Try adding this in your Global.asax
public static void RegisterRoutes(RouteCollection routes)
{
//all your other routes
routes.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL
new { controller = "Home", action = "Index", id = "" }, // Defaults
new[]{"Your.NameSpace"} // Namespaces
);
}