Lately, my iPhone 3Gs is giving problems with charging. The original charging wire worked fine for over a year then intermittently, instead of charging, a black screen appears with a yellow warning stating, "Charging is not supported with this accessory". So I purchased a new charger wire which worked fine for about 3 weeks and now the message keeps appearing regarding it can't charge. I must keep pulling-out the connector from the phone several times and the charging often returns for a while. What's the problem? Is it with the battery? The connector wire is seated tightly with the pins.