For those using authlogic that have had issues with auditing your User model, version 1.0.2 of acts_as_audited should cure your woes.

All you need to do is exclude the last_request_at and perisable_token fields from being audited. We also excluded a few other fields that don’t need to be audited:

class User < ActiveRecord::Base
  acts_as_audited :except => [
    :crypted_password,
    :persistence_token,
    :single_access_token,
    :perishable_token,
    :last_request_at,
  ]
end