Join Date: May 2007
Location: Fairbanks, Alaska
If this just cropped up two weeks ago, I am inclined to go with him being sore somewhere. It could be badly fitting tack. He could have strained something, he could be stiff somewhere. Try to have him looked at, and eliminate soreness.
If tack fits, and he checks out by a vet as not being sore, then I would get more firm with him about the behavior. If you are unfamiliar with dealing with refusals, grab a trusted/knowledgable friend to help; or take a lesson or two just addressing that.
It really depends on the horse as to how you respond to the refusal - different horses require different levels of firmness. What is required to help it sink in with one horse, would traumatize another. On that note; know your horse, and don't let anyone do anything you are uncomfortable with.
Please check for soreness first. You don't want him to feel punished for hurting.