Mine stopped working last night. Menu key works fine. Both menu and back key work with S-Pen. Both work normally in recovery, so I presume it's not a hardware issue. I tried reflashing bootloader, ROM, factory reset. Nothing.
I'm wondering if a certain gesture turned it off (like a hard off)? My finger slid on the Back key maybe also Menu key, S Finder opened up for some reason, and it stopped working. Any hidden combination of gestures, touches, button presses that do this? Any help would be appreciated.