Have you checked if you are in Adventure mode? If so, change to Survival or Creative Mode.
He/She/It is probably trying to break locked blocks. They can't be broken, sorry!
Maybe... Are you trying to Break blocks inside a Dungeon, or on the Dungeon Tower (the big tower with dungeon blocks)?
I have experienced that issue too, the invisible area one, but it does not go away... I could use a little help in the understanding of this
Guys, I wish I could help you with this problem but I never experienced it nor know how to fix it. It seems like a bug related to normal block chuncks being recognized as dungeon block chunks, but I don't know how to fix it...