I am also experiencing this issue. It only occurs on 2a chargers where Settings - Battery reports Charging (AC) rather than Charging (USB) like when plugged into a lower amp USB port. One interesting thing to note is that if you power the S3 off and reboot, it will report (USB) under Battery Settings, but removing and reinserting the cable after booted, it will again show (AC) and the red X reappears; I've actually noted this behavior in the past, minus the red X, as I've found it was actually losing battery power faster than it could charge while using the device for GPS navigation, so I've always looked to make sure it was reporting (AC) and getting the higher charge-rate. I don't think it's a huge issue, since the battery is still charging with the red X, and found some posts indicating that it might simply mean that the device is running off (AC) power and not requiring any input from the battery.