Signing in a user - Chapter 8.2 of Michael Hartl's RoR Tutorial

I'm going through section 8.2 Michael Hartl's RoR 3.2 tutorial and
can't seem to get a user signed in. I've followed the tutorial
exactly, but for some reason @current_user appears to be blank when I
debug and print it out on a view after submitting the sign in form.
I've looked over the code multiple times and can't seem to find
anything wrong. Any help appreciated. Thank you.

(See below for code)
http://stackoverflow.com/questions/12764371/michael-hartls-ruby-on-rails-tutorial-chapter-8-sign-in