Do try ART - (activerelease.com has practitioners probably) - it can work wonders. The basic algorithm is to identify the parts of the muscle that are tenser than the rest, bring the muscle into full flexion, then compress the tense area against the bone while simultaneously moving the muscle into full extension. This causes a mechanical stress that helps lengthen the tissue. You can try it on yourself pretty easily which can be useful.
It does happen though, but strangely only with certain therapists. There is one where I live that is renowned for fixing almost any musculoskeletal issue in one session.
My recommendation would be to find out which one is used by pro sports teams and go to them.
http://www.t-nation.com/free_online_article/sports_body_trai...
1. Go to a paul chek, nasm or shirley sharman practitioner. They will check out your posture. Ignore anything they say about the one true way [edit - I mean the research is inconclusive - either may work, but all will claim their way is correct].
2. If you already have bad posture you need to correct it. Some good [alternative] ways:
- overhead lifting and overhead shrugs
- heavy front squat holds (just the hold, not the squat)
- go look at at mike robertson or gray cook for corrective exercises
3. If you haven't already tried, go to an ART practitioner. It's very sore but effective for a lot of people.