My Rails3 Routing Issue - params are empty

gistfile1.rb

# this is my route
match 'papers/:url_title' => 'papers#show', :as => :permalinkpaper

# this is the url being called
http://localhost:3000/papers/great-passion

# which properly matches to this controller#action for papers#show 
def show
    @paper = Paper.where(:url_title => params[:url_title]).first()
    PaperHistory.add( current_user, @paper.id )
        
    respond_to do |format|
      format.html # show.html.erb
      format.xml  { render :xml => @paper }
      format.json { render :json => @paper }
      format.mobile # { render :layout => false }
    end
  end

# which generals this error because the Paper looking returns noting because the params[:url_title] is nil
Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id

# the log stack trace
Started GET "/papers/great-passion" for 127.0.0.1 at Mon Jan 24 23:04:04 -0600 2011
  Processing by PapersController#show as HTML

  SQL (0.7ms)  SHOW TABLES
  SQL (0.5ms)  SHOW TABLES
  Paper Load (0.7ms)  SELECT `papers`.* FROM `papers` WHERE (`papers`.`url_title` IS NULL) ORDER BY title LIMIT 1
Completed   in 119ms

RuntimeError (Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id):
  app/controllers/papers_controller.rb:43:in `show'



# I've validated the route in the console and it seems to know :url_title is the proper value
>> r = ActionController::Routing::Routes
>> r.recognize_path "/papers/great-passion"
=> {:action=>"show", :url_title=>"great-passion", :controller=>"papers"}

# I'm at a loss!