Well that really stinks, I just finished reading all the other posts. What an awful trainer. Sounds like she clearly undid any training you did.
Here's what I'd do.
First call the vet, get blood work done. Morgans are very easy keepers, they don't do well on hot feed. My mare is a Canadian (the ancestors of Morgans, essentially a draft Morgan) I just needed to completely eliminate grain from her diet and replace it with a Ration Balancer (Thanks DesertHorse for teaching me!). Personally, if your boy is an easy keeper and is on any sort of grain I'd switch him over to a ration balancer instead. Talk to your vet about feed options. They'll also probably take blood tests, you'll want to know particularly about deficiencies in Magnesium, Selenium and B1. I had to supplement my mare with additional Magnesium and B1. So figure out his diet and give it a couple months to really show the full change. I have seen radical changes in my mare in less than a month, I've alsostarted her on Omega 3's which has made her allergy to bugs less severe, I mention this because it's a common problem in Morgans too, if that's affecting your boy it may be causing him extreme discomfort. My mare knows bugs cause her to be miserable, she won't leave her run-in stall once the sun starts going down. If you work with him later in the day when the bugs are bad his nerves may be up. They tend to get anxious and flighty when their incredibly uncomfortable from the itchies.
In the meantime continue his ground work, work him again until he's yielding every inch of himself readily with just your focal cue. Meaning you move into his space and imply that you want him to move, meaning you don't even need to touch him anymore.
Then I'd work on lunging again, when he's responding again to your verbal and focal cues, reading your body language and being respectful, I'd begin line-driving. This means driving him around from the ground behind him, obviously without a cart or anything, and stand sort of to one side. You can use the saddle rings or stirrups to run two short lunge lines through, don't use one so big you'll get tangled up in. Start by lunging him at the walk with the two reins, then, using the outside rein, ask for short straight lines. Repeat this until you can ground drive him quite well all around, just as if you were riding him. Eventually you can practice this on trails too, if you're comfortable. But at that point it's time to start backing him again. He clearly knew how to be a good horse, he still knows, he's just hot. So, I'd check his feed and make sure there's no deficiencies, repeat his skills, it'll probably go much faster than the first time, then work on line-driving. Line-driving is great for letting little things show up that would only show up when riding, little things that could be big things if you were on his back.
I'd also, if you can afford it, look for a trainer who can come to your property and teach you how to work with your horse. No real trainer is completely dependent on an arena or round pen. If they say they need one they're not worth hiring. They're beneficial tools that may speed things up but they aren't needed. You should see if there's a trainer who will let you do the work, that way you can learn and build your own confidence, but with the assurance and guidance of a professional keeping you safe.
Good luck, I'd love to see pics, I love Morgans!
ETA: This may sound obvious, but I'd also check his tack. A horse's body can change a great deal in a year, especially a year out of work - he could just be rebelling against ill-fitted tack?
Last edited by PunksTank; 09-30-2012 at 12:41 AM.