A few non backwards compatible changes have been made that are really easy to fix.

If you are upgrading a oauth_consumer from 0.3.x to 0.4.x add the following line to your consumer_token model:

  belongs_to :user

So it looks like this:

  require 'oauth/models/consumers/token'
  class ConsumerToken < ActiveRecord::Base
    include Oauth::Models::Consumers::Token
    belongs_to :user
  end

You should also upgrade your oauth_consumer_controller as we no longer call login_required in the library. This should make it easier for implementing it with other authentication frameworks:

  require 'oauth/controllers/consumer_controller'
  class OauthConsumersController < ApplicationController
    include Oauth::Controllers::ConsumerController
    # Replace this with the equivalent for your authentication framework
    before_filter :login_required, :only=>:index