It could have just been the day, but I would check and make sure the cinch is not pinching the horse, and make sure it is the right size. It maybe that since you changed the pad that the cinch is not fitting properly and pinching somewhere or digging in. I would start with that. Maybe put your old pad back on and see what happens. Also, I would make sure that the saddle fits properly. You could also try a different style cinch. I for one prefer 100% mohair roping cinches. I found that in the summer the neoprene cinches tend to pinch the skin more and rub sore spots. Since using the mohair I have had no problem. Hope this helps if I think of anything else, I'll post it.