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 <profile defaultProvider="SqlProvider" inherits="YourNamespace.AccountProfile">
section.
<profile defaultProvider="SqlProvider" inherits="YourNamespace.AccountProfile">
<providers>
<clear />
<add name="SqlProvider"
type="System.Web.Profile.SqlProfileProvider"
connectionStringName="sqlServerMembership" />
</providers>
</profile>