I recently opened my iPhone 3Gs to replace the screen and digitizer. Soon after, I realized that the proximity sensor was not working - the screen would remain on and active during calls while I held the phone to my face. My initial thought was that the problem must be something other than the proximity sensor cable, since this same cable controls the earpiece, and my earpiece works just fine. I thought the problem might be that the aftermarket replacement screen was too dark over the proximity sensor, so I opened the phone back up and used a razor blade to scrape the inside of the screen above the proximity sensor to lighten it. That did not work, however, and the proximity sensor is still broken. Does anyone have any thoughts on what the problem could be? Is it possible that I've damaged the proximity sensor/earpiece speaker, but in such a way that it only affects the proximity sensor while leaving the earpiece functioning? Do you think my next diagnostic step should be replace the proximity sensor/earpiece cable, or is there something else I should try first? Could it be a software issue? Thanks!