Authlogic plugin for MongoMapper

authenticable.rb

module Authenticable
  extend ActiveSupport::Concern

  included do
    key :username,          String
    key :email,             String
    key :crypted_password,  String
    key :password_salt,     String
    key :persistence_token, String
    key :login_count,       Integer, :default => 0
    key :last_request_at,   Time
    key :last_login_at,     Time
    key :current_login_at,  Time
    key :last_login_ip,     String
    key :current_login_ip,  String

    class << self
      alias named_scope scope
    end

    include Authlogic::ActsAsAuthentic::Base
    include Authlogic::ActsAsAuthentic::Email
    include Authlogic::ActsAsAuthentic::LoggedInStatus
    include Authlogic::ActsAsAuthentic::Login
    include Authlogic::ActsAsAuthentic::MagicColumns
    include Authlogic::ActsAsAuthentic::Password
    include Authlogic::ActsAsAuthentic::PerishableToken
    include Authlogic::ActsAsAuthentic::PersistenceToken
    include Authlogic::ActsAsAuthentic::RestfulAuthentication
    include Authlogic::ActsAsAuthentic::SessionMaintenance
    include Authlogic::ActsAsAuthentic::SingleAccessToken
    include Authlogic::ActsAsAuthentic::ValidationsScope

    acts_as_authentic do |c|
      c.login_field = 'username'
      c.merge_validates_uniqueness_of_login_field_options :scope => '_id', :case_sensitive => true
    end
  end

  module ClassMethods
    def base_class
      self
    end

    def primary_key
      :_id
    end

    def default_timezone
      :utc
    end

    def with_scope(qry)
      qry = where(qry) if qry.is_a?(Hash)
      yield qry
    end
  end

  module InstanceMethods
    def save(options = {})
      options = {:validate => options} unless options.is_a?(Hash)
      super
    end

    def readonly?
      false
    end
  end
end

user.rb

class User
  include MongoMapper::Document
  plugin Authenticable

  timestamps!
end

user_session.rb

class UserSession < Authlogic::Session::Base
  def to_key
    new_record? ? nil : [self.send(self.class.primary_key)]
  end
end

FYI, I am using this guide for the rest of AuthLogic / Rails 3 : http://www.dixis.com/?p=352

I'm occasionally now getting this issue when I create a new user in the system:

NoMethodError (undefined method []=' for BSON::ObjectId('4e6e5c8414a6940001000006'):BSON::ObjectId): 2011-09-12T19:24:52+00:00 app[web.1]: app/models/authenticable.rb:58:insave'
2011-09-12T19:24:52+00:00 app[web.1]: app/controllers/users_controller.rb:4:in `create'

The error isn't consistant. I can get it to fail when I deploy on heroku+mongohq, but it doesn't fail when I run it locally (with a local mongodb).

Any ideas?

I'm getting the following error:

undefined local variable or method `model' for User:Class

With Rails 3.1.3.

i getting the following error:
uninitialized constant ActiveSupport::Concern (NameError)
with rails 2.3.11 and mongomapper

I'm getting same error with spockz...
How should i fix that error?
Thanks.