I had the same problem except the horse would only move backwards. at first she wouldn't walk at all... then I had her owner come out and lunge her. She kicked and bucked and reared on the lunge line to get out of moving forward. I couldn't use a crop on her cause she would do little bucks every time I did.
Anyway, we got her trainer to come out and with just a few rears and a couple kicks she lunged. After that i was able to get her to walk forward but not trot or anything. I left it at that.
I don't think I am going to see her again. I was going to lease her but I am thinking now I am just not experienced enough.
So yep... That doesn't help at all I guess but ... now you know.. it could be worse! haha. At lease he lunges! :P