Can he be turned out with another horse? It sounds like he may be very very herdbound, and that is why he won't stay in the fence.
Have you tried putting an electric strand over the fences, and teaching him a healthy respect for them? I know for a jumper, that may or may not work; it did help a snotty pony cross I had when I was growing up...he daily tested that strand too, to see if it had been turned on...scary smart! If it wasn't on, he would lean, or try to jump!
I would not simply be walking this horse around for exercise...invest in some lungeing equipment and start working him to actually get rid of some of that energy...if he can't be turned out you have to do more than walk him! I would think someone at that stable should be able to help you get him lungeing.
It sounds as though he may have been drugged, OR he is just reading you as a handler, and has decided you aren't strong enough of a leader for him, so is being a snot as a result...see if you can't have a trainer come out and both watch you handle him, and be able to give you ideas on how your handling may be effecting his behavior, and help you make the proper adjustments to help both you and the horse.
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."
Last edited by mom2pride; 01-03-2011 at 12:31 AM.