I had the same problem with my 4s until I read somewhere in these posts that a dirty (headphone) connector may be involved - I had an unrelated problem, where my iPhone connected through the Apple connector to my car stereo would skip to the next song, every time I hit a bump in the road (that's when you realize how many bumps there are in the roads...) - very aggravating while you are in your favorite song! As I have my iPhone in my pocket all the time, I realized that with time lint settles in the connectors and prevents the connector to engage properly. Cleaned the connector carefully with a toothpick to get the lint and dust out, and voila - I can enjoy my music again without skipping a beat!
But I digress... So today, I took a professional electronic contact cleaner spray (I'm fortunate enough to work in a company where we have this stuff around) and sprayed it into both the Apple connector on the bottom and the headphone connector on top, and low and behold the problem was gone. So much for the theory that it is an Apple OS software bug... after all the 4s has been around for a long time and chances are your's got dirty too and just needs a good cleaning!
Anyway, if you try this, make sure you use a NON-CONDUCTING, RESIDUE FREE, professional contact cleaner, and don't overdo it, or have your Geek squad do it. You don't want to spray anything in there that shorts out your phone's electronics and causes more harm than good.
Good luck! I hope you all get your sound back
