I'm on the road (Australia) and a LONG way from my Apple Store in Seattle WA. Today I plugged my XS into a socket using the iPad block charger and didn't get any indication of charging. Tried reversing the block charger and reversing the charging cable without getting the "lightning" bolt indicating charging. Tried my wife's IP and using the same cabling, hers immediately showed charging. Rebooted the phone and still no charging. Then I got a message that said something like "unlock phone to use USB connection". I should have written the exact error message down. The phone was unlocked when I got this message. I then one more time, pulled the block charger out of the socket and reversed it (for no good reason). As soon as I plugged it back in, I immediately got the charging "bolt" indication. I've seen this error message once before. Since all the same cabling was used with my wife's phone, I assume this is not a cabling problem. Anyone else seen this "USB" error.