The problem is solved! My instructor and I met before class last night and, basically, took time to micro-adjust one of the spinning bikes for me (not one of the new ones). Voila, no hip/groin,thigh pain at all and am VERY happy about that. I was starting to be concerned that my clipless gymnastics a week ago had perhaps damaged something as this was on the same side that kept hitting the ground rather hard (I know better than to catch myself with my hand).