I've owned a powered USB 2.0 hub for several years now, and plug my iPhone in to charge or sync it with my computer. Sometimes when it just sits on its own, and charges, a message pops up on the phone telling me that this device is not supported. Is there some way to fix this, or should I buy a supported USB hub instead? Any of them designed to work correctly with the iPhone? I'd rather not get a multi port charger, because a USB hub is of more use to me...