I\'ve been using ASP.NET MVC with membership-based login for several years and everything is working fine (it\'s now MVC3, but membership didn\'t change since the first version
Joel Spolsky had a great answer to this question on this post. You're basically on the right track.
If you're getting the illegal cast error, its most likely due to a problem in the config file. Make sure this is included; more specifically the section.