I encountered the same issue and after poking around I tried
class ApplicationController < ActionController::Base
helper :all # include all helpers, all the time
protect_from_forgery # See ActionController::RequestForgeryProtection for details
# Pg. 206 - Doesn't work in Rails 2.x
# model :cart
# model :purchase
It got past the error, not sure if it is doing what it is suppose to or not.