This may seem overly simple, but have you considered muscle imbalance? It is often the source of incorrectly diagnosed problems, I experienced this with prolonged neck issues following a whiplash injury. For the longest time I would have neck soreness and could not stop rubbing it. What helped me was 5 sessions of prolotherapy to treat the damaged muscles, then muscle imbalance correction with simple gym exercises aimed at re-activating the muscles that have become stretched out, and by stretching out the muscles that have gone tight.

For me, i found that my chest was extremely tight (pulling in), and my mid back muscles weren't activating. As a result, my neck muscles were pulling down and was were i had become symptomatic. I'm not too sure if the prolotherapy was completely necessary, but treating the muscle imbalance was how i recovered. There are lots of good workouts posted on the internet that offer good muscle imbalance workouts. The key is to start with body weight at very low reps and only a couple sets per day.

For some background reading, Dr. Phil Maffetone has written extensively on muscle imbalance. I learned about prolotherapy through my naturopath, but there is good information available on the web, if you filter through all the garbage (including the negative information). Muscle imbalance correction is easy to research, even Men's Health Magazine can be trusted with this.

Cheers,

Hains