Be careful about using compressed air and desiccants. I've repaired two iPhones with the same issue by using a sonic toothbrush to shake the moisture and dirt from the earpiece. Simply place the bristles directly on the earpiece grate and turn the toothbrush on high for a few minutes. It will dislodge all the buildup and your phone will be as good as new. One of my phones had been submerged in a sink for about 10 seconds and this fixed the issue while compressed air and desiccant had no effect. Update (12/09/2011): Bryan's solution, the sonic toothbrush (I simply used a mechanical one) actually worked! I cannot even believe it, my jaw just hit the floor. THANKS BRYAN! (still stunned this worked.... I thought, there was no way)