Girl! I am so sorry! I have a theory (posited briefly in my blog) that the additional ROM in the new hip stresses the muscles and soft bits that had learned to accommodate the limitations of the old hip. Clearly, I'm just making stuff up (see my signature), but could this be related? Was your psoas sore before surgery?
This may not be accurate or even helpful, but it seems like a fair number of people have knee/groin issues 2-4 months after surgery, me included. So maddening!
I used to get psoas pain when I'd ride too hard and too far, since my shoes clip on to my pedals, and I can pull up to help power up hills - holy moly, that hurt!! It felt like they'd been lit on fire!