On my Motorola xoom which is android 4.1, when I click in TextInput soft keyboard popuped. Then I switch input method by click on 'settings' button, and then, click system 'back' menu to return to application. Next time, when I click in TextInput, soft keyboard popup as usual but the screen goes 'black'.
I found a clue -- it happened only when I new a flash.media.Video object, if not, never happened.
Another clue, must set TextInput skin to spark.skins.mobile.TextInputSkin.