how long have you have them for? i would look at the warranty card/booklet that came with your ipod to read the terms/conditions on accessory coverage. this would also be a perfect oppertunity to buy some headphones/earbuds that will allow you to enjoy your ipod the way it was meant to be enjoyed. The bundled ipod earbuds sound bad and as such many people replace them right out of the box.
either way, good luck.