Surely you've seen the green robot that accompanies the "android update." My S4 gives me that and hangs. I've let it go over 12 hours and it's still hung. I remove and reinsert the battery and the phone works for awhile until the same thing happens again. I'm not convinced this is really an update for such an old phone, plus I have two purchased at the same time (his and hers) and the other one works fine. Any ideas?