I was working with an Icelandic who did exactly that. Stopped dead. It really helped to clicker her for any forward motion. If she was stuck, I'd try to get her to move even one front foot and click. If I couldn't get her to step straight forward, if I got her to step slightly to the side, I'd still click and treat. first just for a few steps each time, then more and more. It would probably help to still do the carrot things for a double incentive!
Cherie
