I am having some issues with the car charger that I bought from Amazon. It is a dock connector that splits into a usb cable and aux output. When it works, I love it. It worked very well for a while, but recently, when I plug it in I have no idea if it will charge. Sometimes it will start charging and then a few minutes later stop and say "charging is not supported with this accessory", other times it wont charge at all and then randomly start charging along my ride. Why is this happening? Is there anything I can do to fix it, or do I need ot buy a better cable for my iPhone 4?