Rails - Mar 2012 - Nested Attributes not Working in Form

I have a form that uses two models - badge and badge winners. The user_id 
and community_id fields are needed for badge_winners which is nested in 
badges.  I was trying to learn from Ryan Bates'' Railscast (
http://railscasts.com/episodes/196-nested-model-form-part-1)

The error I''m getting is: 
ActiveRecord::UnknownAttributeError in BadgesController#create
unknown attribute: user_id

app/controllers/badges_controller.rb:42:in `new''

LIne 42 corresponds to this line in :create
@badge = Badge.new(params[:badge])

*here''s the controller:*

  def new
    @badge = Badge.new
    badge_winner = @badge.badge_winners.build
    respond_with(@badge)
  end

  def create
    @badge = Badge.new(params[:badge])
    if @badge.save
      flash[:notice] = "Badge was successfully created."
      redirect_to home_path
    else
      flash[:notice] = "There was a problem creating your badge."
      redirect_to home_path
    end     
  end


*Here''s the form (both community_id and user_id are populating fine):*

<%= form_for(@badge) do |f| %>

    <%= f.label :Description %>
    <%= f.text_area :description %>

    <%= f.fields_for :badge_winners do |builder| %>
         <%= builder.hidden_field :user_id ,:value => user_id %>
         <%= builder.hidden_field :community_id ,:value => community_id
%>
    <% end %>

    <%= f.submit "Give Badge" %>
<% end %>

*The models (user_id and community_id are fields in the BadgeWinner table):*

  class Badge < ActiveRecord::Base
     belongs_to :community
     has_many :badge_winners, :dependent=>:destroy
     accepts_nested_attributes_for :badge_winners
  end

  class BadgeWinner < ActiveRecord::Base
    belongs_to :user
    belongs_to :badge
  end

I''m hoping someone''s able to help.  I just know it''s
a newbie error
somewhere.  Thanks in advance for any assistance! 

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