Originally Posted by Faux_ghost
it is completely stock un-rooted rom from the at&t OTA update
Since its completely stock, yes you have to reset it. Factory Reset but not from the settings. I have been in the same situation before and I tried resetting it from the Recovery Mode which eventually helped.
Backup all your contacts, media files from your devices storage, S Notes (if not backed up by your Samsung account and other important files from the storage. If using a SD card in the phone, do backup ur media and just format it from your PC. Then reinsert it in the phone, turn the phone on using Recovery Mode (Vol Up + Home Btn + Power Btn) and Clear/erase the cache and then reset it. Turn the phone on if it doesnt automatically, set it up according to yourself and voila it would eventually work. Format ur SD Card using ur phone now and move all your data back in.
the problem I see is that there must be something unwanted and it installed on the device which causes various issues just like a virus. I hope this will help you out. I have done it on S4, S3 , Note 2 and Galaxy Grand and it did help me and my friends out. The same problem was there to deal with. Try it! Let us know if it worked.