Product review (5 stars): Try this before calling for service.
Problem solved within 5 minutes. It took me 4 iterations (fill syringe, squirt into line) to unblock my line, but it worked and with way less drama than the alternatives (the hair dryer trick, shutting down/defrosting refrigerator for a day, etc.) My only regret is that I didn't discover this product before wasting money on an unproductive service call.