My 8330 is 2.5 months old. After it wouldn't connect to the computer I tried it with two chargers and it wouldn't show that it is plugged in. I took out a new usb cable and used that and it worked. If the usb port had a bad connection that would make sense that the unused usb cable was probably a little tighter than the other three cables that are used regularly. I backed up the phone and took it to a Sprint repair facility assuming it needed the port replaced. I picked it up two hours later and they said it had a bad battery. I thought that was unlikely to cause those symptoms, but I took it home and it works perfectly every time.
