If you install Perian, QuickTime will be able to play flv files normally. Since iMovie is QuickTime-based, it should then be able to import them (I think; I don't have much experience with iMovie, though).
If you install Perian, QuickTime will be able to play flv files normally. Since iMovie is QuickTime-based, it should then be able to import them (I think; I don't have much experience with iMovie, though).