I had that same problem with my S3 after the jelly bean update. Then a few after the update my copy and paste stopped working and the phone was performing really sluggish. So I did a full reset on the phone which sorted out the problem.
But a few days after doing this my started to reset on it's own which it never did that before, then one day when i got home from work i heard my phone get a notification so when went to the phone to see what it was my phone was stuck in the Samsung galaxy start up screen I pulled the battery out the phone put it back in and still the same I could not even put the phone in the recover mode but I could put it in the download mode but could not flash the phone or anything. Sent my phone back to Vodafone then they phoned me to say I had rooted my phone and to fix it they will have to charge me 100 quid I told them the phone had never been rooted and it was updated via Kies but they was having none of it. So I told them send my phone back un-repaired which they did! in the end I went to a walk in Samsung repair center they took the phone and said they will have it for 48 hrs to check out the fault. a few hours later had call from Samsung repair center saying they had fixed my phone and said they had to replace the motherboard and that the phone now virtually brand new. So if I was you I'd take to Samsung and get the phone checked out!