I've just started getting this problem on my 2-month-old iPhone 4s. I get audio from my SatNav app and alert notification sounds, but nothing from Music, or YouTube, or iPlayer, or Skype, or any of my other apps. Normal phone calls seem to work okay - I don't make that many. But with skype calls I can't hear the other person (I used to be able to).
I've tried:
- killing all active apps
- turning the audio switch on/off/on
- cleaning the docking port with a toothbrush.
- doing the weird thing someone suggested: playing something with headphones in, then plugging in the charger, then taking the headphones out, then pressing play, then taking the charger out again. I think the theory there is that it re-sets the software somewhere.
About to try:
- backing up and restoring the phone.
Any other suggestions out there?