IPhone 4S won't connect to charger?

I got my iP4S at Christmas, and it's never been troublesome at all. I charge it every night without fail, and if the charge is running low during the day then I'll simply connect it.

The charger is fitting in perfectly at the bottom, but the 'charge' bar is showing no signs that it's connected. The plug is fine, the cords aren't loose, there's no dust in the section where the charger actually goes in. What's going on with it?

It's still under warrenty so try taking it to an Apple store near you