I haven't yet been to the imps world.I think I was just covering ground near The Warrior's Guild and had got a full load and I went back to Ars Mag to sell some stuff (I have one stone there) and when I went to use my stone in Ars to get back to the one I dropped I got the message.Fortunately the one I dropped was near the Teleporter at Warrior's so I went back that way.But anyway ---- Having read all this I recently tried my stones again and they now have decided to work again!! Maybe there are a few "blackout" zones as you say.