Hip flexor pain when extending in a V

Basically, I have a really hard time with anything where my legs are extended in a "v" and lifted. It seems to only be an issue in the open, lifted position. A V on the floor doesn't hurt, but a V with my legs lifted does (as in the wrist seat). Lifting my legs in a pike position doesn't hurt, but extending them out into a V is killer sometimes! I get a similar pain from the cross ankle/knee release sometimes, strangely. It doesn't happen all the time, but sometimes I have to take a few days off from those types of moves when my hips are acting up.  I recognize the pain as being in my hip flexors, sort of "inside" my leg on the front of my hip. Frequently my legs lock up and need to "pop" out of place as well at the hip. I have no clue what the problem is, and I haven't been able to find anyone else who has the same issue or knows what to do about it. Could it be a sign that my hip flexors are weak or inflexible? Or perhaps another weak muscle and I'm overcompensating with my hips?