What's With the Mare?

So since right around New Years, Cadence has been acting a bit strange.  It started off with her being a little tense during downward transitions, then she started to stiffen during downwards transitions, and before I had time to really register what was happening she had morphed into a full blown temper tantrum throwing nutbar.  This (naturally) surfaced when we went up to my coach's friend's farm (who also happens to be a two time Olympian, among other accomplishments) for a dressage lesson.  I still haven't posted the video from that day because my computer has run out of disk space, so it's stuck on the camera. Anywho, that was mid-January and we're still working through this bout of hyperactivity and attitude.

Originally, I blamed things on Cadence being in heat, and us upping the pressure on her dressage work by increasing the amount of lateral work and collection that was expected of her.  Then, I blamed it on an increase of energy due to the cold weather (which prevents them from being basketcases out of doors) and copious amounts of second cut hay- a reasonable conclusion to draw as she never protested to upwards transitions... only down!  I'd ruled out saddle fit issues, back soreness, and as she wasn't acting like it was a pain issue, teeth didn't seem likely either.  However, I'm beginning to doubt my original conclusion that teeth aren't the issue.  This original epiphany came when Cadence was flat out refusing to halt... until out of desperation I jerked back on the neck strap of her running martingale.  Then, miracle of all miracles she stood! Also, unlike your standard attitude issue, she's perfectly polite on the ground. I free lunged her today, and she would halt and back up off voice commands with me half way across the ring.... so maybe its not as attitude related as I'd originally thought.  It has only been 9 months since her teeth were last done, but she has an exceptionally small mouth (and is still relatively young) so the vet did warn me that her teeth may need more frequent attention, and alhough I'm generally pretty good at guessing what's going on with miss Mare, I'm as prone to errors as the next person.  So I set up a vet appointment for next week to get Cadence's teeth done, AND her vet check for travel papers!  Yay!!! Hard to believe it's just over a month until we leave....