"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 CS6, but it work well in CS5 and CS5.5 (for CS3 and CS4 please use flt-cs4). Forget all "solutions" that work with published format ".swf" - this extention is searching all text that should be localized in your source ".fla" files, it can exports Action Scripts and it is able to export parameters from components used in your flash file.
New version released - flt-cs6 3.10.31. Now working with Adobe Flash CS6.