Flash Localization Tool in it's latest version is the best solution how to localize your Flash applications. You do not have to be an Action Script expert or have localization experience to be able to get your application localized.
Tool is primary developed for Adobe Flash CS3, but works well under Flash CS4. Forget all solutions that work with published format. swf - this extension scans the source fla files for all texts that should be localized, it can easily exports Action Scripts and it is able to export parameters from components used in your flash file.