1. Friendly, affectionate, confident, pocket-pony type horse; I've owned him for about seven years and have never once had trouble catching him. Loves people, loves attention.
2. May or may not be relevant: Yesterday morning he had his teeth done. Seemed find afterward. Ate dinner/breakfast fine, eating hay fine.
3. This morning there is something very wrong. I turned him out (he seemed fine at this point) and went in to do stalls. I peeked out a few minutes later and he was in the center of the paddock, standing stock still, and not eating the hay. I kind of watched him while doing stalls, and by the time I was done he was eating, so I left. Came back 2 hours later and he was chasing his mare around (usually an indicator that something has upset him). I went in to see what was wrong with him and he was AFRAID of me. Never in his life has this horse been afraid of people. Would not let me near him--would spin and run. I finally got him to let me touch his face, but when I tried to touch his neck he spooked hard and ran away. He was not being stupid--he was scared. It's pretty clear that something in his neck or head HURTS and he doesn't understand what's going on.
I called the dentist and she said she'd never had anything like this happen before, but if he's still funky tomorrow, she will come out and see if she can see anything.
He may have a strained, kinked muscle or some other connective tissue in his neck, face, poll. Depending on how she did his teeth, he could even have a strained back. Did he pull back or resist during the procedure? Did he get a sedative?
I have discovered that a change in behavior is almost certainly pain-caused. You could give him 2 grms of bute as a diagnostic...if he gets better you can be sure it's pain. Assuming he doesn't have any problems with bute, of course.
He did resist quite a bit while having his teeth done in the form of walking in circles around his stall/backing into the corners, etc. The dentist prefers to let them move and just follows them around while she works. He was not sedated.
He seems somewhat better today... in his stall he seemed totally fine. I groomed him all over while he ate his grain, and it was a non-issue. I made a point of rubbing all around his poll and ears, even inside his ears, with no response except "ooooh, itchy!" Out in the paddock, he still won't let me near him but isn't panicky about it. Guess I'll give it another day...?
If I could remember every detail of having my mouth pried open and my teeth sawed away at.....well, I don't think I'd want to be caught either!! I think he's traumatized and doesn't want anymore attacks on his mouth!