If you look at the bottom of the iPhone 5, you should see a metal "ring" which is where the Lightning connector inserts. On my black iPhone, the connector is a slightly different color than the metal at the bottom of the iPhone. The while cable has nothing black on it at all (other than my cable wrap I use to keep it "tidy"). I know that my wife had managed to get something (paper/cardboard shreds) in her connector on her iPhone and that was preventign the cable from fully inserting, but we got those removed with a fine pair of tweezers. The only other thing I csn think of which might be causing your issue is that your case might not be fitted properly for insertign the cable while in the case. I have seen this with some of the adapters, like the third party micro-USB to Lightning, or the 30-Pin Dock to Lightning adapters. I don't have this issue with my iPhone in the iFrogz case, or my wife's in her Speck case.