On my s3, I am having the red x issue. I have also noticed some other things. My phone has showed that it was not charging on the icon but the LED shows it charging and it charged just fine without the red x. I have a wall/car combo charger that has dedicated 2.1amp and a dedicated 1amp usb port. On the 2.1amp side it did not want to charge. After fiddling with it i got it to show red x and sometimes charging. On the 1amp side it showed charging but was intermittent.