Nunca mexi com o authlogic, mas entendi o que vc disse.
Dei uma pesquisada no AuthLogic e por alto vi que ele tbm da suporte a internacionalização das mensagens de erro dele.
não sei se te ajuda, mas se colocar mais algumas chaves no pt-BR.yml dá pra modificar umas mensagens do authlogic
authlogic:
error_messages:
login_blank: can not be blank
login_not_found: is not valid
login_invalid: should use only letters, numbers, spaces, and .-_@ please.
consecutive_failed_logins_limit_exceeded: Consecutive failed logins limit exceeded, account is disabled.
email_invalid: should look like an email address.
password_blank: can not be blank
password_invalid: is not valid
not_active: Your account is not active
not_confirmed: Your account is not confirmed
not_approved: Your account is not approved
no_authentication_details: You did not provide any details for authentication.
models:
user_session: UserSession (or whatever name you are using)
attributes:
user_session: (or whatever name you are using)
login: login
email: email
password: password
remember_me: remember me
Claro com o texto em Portugues.
Até!