My iPhone 4 only charges with a wall outlet. I have had this phone for a year or so, never had a problem with it charging. Out of nowhere today, it will not charge with any cord, on any computer. I have tried 4 different PC's with 4 different OEM cords all with the same result. Nothing. But, I can plug my phone into a wall outlet and it charges fine. I tried this with the same said cords that would not charge when plugged into a PC, all worked fine via wall adapter. These are the same PC's I have used to charge my phone since I bought it, they have always connected and charged fine. There was nothing done to the phone to bring this on. No damage, no drops, no liquid, etc. Any help here? Thanks