Apple fitted a small chip into the head of the adapter on its lightning cable.
When you upgrade to iOS 7 this chip can be read and very often you'll get a message saying that the cable isn't a recognised device, this is because Apple don't want people using the cheaper generic cable.
The good News
is that your original cable has a 12m warranty on it the same as your phone, so if you take it back to Apple (and the phone is still in warranty) they'll give you a new one.
They're replacing cables all day long, the lighting adapter is not a good design.
Don't try returning a copy, they can tell the difference.