Starting with Grails 1.3.4, any property files added to the grails-app/i18n directory will be added to messageSource .
Also, if you try to manually add a bean (and base names under it) when you go into the production environment, it will not load them. It will work in development mode (tested when starting IDEA 9.0.3 and the tomcat v1.3.4 plugin), but not in production mode.
This happened to me after the answer provided by @rochb (I checked the answer and implemented it before the simplest way), and I had to remove the messageSource bean configuration in order to fix it.
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