I've experienced problems with both my iPhone 3G and my iPhone 3GS, where the remote on my Apple headphones has stopped working. I'd assumed it was an issue with the cable but turns out that this is not the case. I can't take the credit for this info as I found it online after doing some Googling, but it turns out that the
Clearing the fluff (and therefore curing the problem) is easy. Just turn your phone off and gently use a pin inserted into the headphone socket to root around and extract the fluff. Hey -- presto -- your remote (and/or mic) will work again!
I was very surprised at just how much fluff had collected in my headphone socket, and suspect the same may be true for anyone else who regularly carries their phone in their pocket.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20100413065648921