I'm not in Adventure Mode, but I must use the right tools to destroy blocks. It does it at some points while I am playing, and then it stays like that and don't know why. Does anyone know what i am on about?
Try check this thread out: Blocks won't break unless with right tools?
Are you sure you are not in adventure mode? If it happens in single-player, then try to make another world and see if it's just that one save. If it's on a multiplayer server, then try another to test, if it's the same.