Hi All,
I agree totally with Noel Br - there are loads of 'I've fixed it' and 'totally worked for me' shouts from folks who've had a quick results from the bit of paper od cardboard or paper 'fix', but isn't a fix at all, just a temporary solution to what is essentially a manufacturing defect. The audio IC, as Noel says, is a BGA device, and not really repairable by man-in-the-street, as it requires some specialised kit to achieve. I'm also well hacked off at Apple for their failure to warranty against this kind of issue - it's a result of poor quality control at manufacture. sorry guys, but it has to be said!
Cheers,
Mel