Nokia :: 6700 No Audio Heard Coming From Music Player App?

Occasionally, when I plug in the supplied headphones which are marked as model number "WH-101 HS-105", there is no audio heard coming through them. When I plug them in, they are detected and a message says use phone mic for calls. However, there is no audio heard coming from the music player app. If I unplug the headphones the music player audio comes out loud and clear from the loudspeaker.The only solution is to reset the phone, the headphones then work correctly and I can listen to music through them. This makes me think it is a software / firmware problem rather than a hardware problem.I sent my phone and the headphones back to my operator O2 UK and waited 4 weeks for my phone to return. They eventualy returned my phone with a note saying a new circuit board had been fitted and the phone would have a new IMEI number.The fault returned the first time I plugged in my headphones!I have looked for info on this fault on the web, but have not found anybody else with this issue to date.