Hmm, we've got a new cable as my Mrs recently got a new iPhone, pretty sure it's still the same problem, although I can't ever be 100% sure what cable I am using in the house. Either way, she has no problems with any of the chargers.
Had two iPhones now and both have ended up with charger-socket connection issues. You can take it to the apple shop who will remove fluff/dirt etc (or do it yourself) but this doesn't seem a permanent solution, towards the end of the 2-year life of my old one and now with my current I've had to...