This problem may not be specific to rFacebook, but when I added acts_as_facebook_user to my user model and then made a call like:
my_user.first_name </pre>I would get an 500 internal server error. I checked the log and saw this: CGI::Session::CookieStore::CookieOverflow I found that if I changed the app so that it uses db sessions everything started working. Uncomment this line in environment.rb:config.action_controller.session_store = :active_record_store </pre>Make sure to add the session tables to your db by using the rake task and you should be good to go. Note that I am running edge rails so keep that in mind if you use this advice.