Jumping Good, Ground Poles Apparently Paralysis Inducing

I had a lesson today, following our little show debut. We spent quite a bit of time working on how to get round and forward simultaneously with good results at the walk and trot and some improvement at the canter. Then on to jumping. He was quite forward and happy to jump everything in the ring (including oxer with blue barrel under it). When we got to the one stride, we had a couple reasonable gos, then he started to leave long, decided that was a bad idea, put his feet down, then failed to lift them up high enough, resulting on catching the pole between his legs, going down almost to his knees, tipping me onto his neck, but then somehow patting the ground and jumping the out! Like Bobby Meyerhoff's "Million Dollar Horse" over much smaller fences http://www.youtube.com/watch?v=kJd-U8w_6bw. He then continued happy to jump, but seemed to think the way to avoid landing on them was to leave out a big stride, slightly unclear on that concept. So, Missy put 3 trot poles in front of a crossrail. Finn trotted up and stopped in total consternation. Missy ended up leading him through at a walk. Then he walked through once, then stopped and was led through again. When Missy widened the poles a bit (from about 2 feet between to 4 feet between), Finn bounced perfectly through them. This was repeated about 4 times, then Missy set them to about 3 feet, resulting in a shuffle through (no poles touched, but really random foot placement), then some combination of trotting and bouncing for the remainder of attempts. I'm having big fun with the boy!