Rails - Jul 2012 - TypeError in FacebooksController#create

I am using fb_graph gem to post something on my wall. I am getting this 
error while using fb_graph -can''t dump hash with default proc. This is
the
code -

def show
  auth = Facebook.auth.from_cookie(cookies)
  authenticate Facebook.identify(auth.user)
  redirect_to root_url
end

# handle Normal OAuth flow: start
def new 
   client = Facebook.auth(callback_facebook_url).client    
   redirect_to client.authorization_uri(
     :scope => Facebook.config[:scope]      
   )    
end

 # handle Normal OAuth flow: callback
def create
  (0..2).each do
    begin
      client = Facebook.auth(callback_facebook_url).client       
      client.authorization_code = params[:code]
      access_token = client.access_token! :client_auth_body  
      user = FbGraph::User.me(access_token).fetch 
      authenticate Facebook.identify(user)  
      redirect_to "/"
      break
    rescue Exception => e
    end
  end
end

I am getting TypeError in FacebooksController#create

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