I phone Charging help!

[graemewh]

I have an I phone 3gs had it just over a year and now the USB charger is becoming dodgy with the message charging is not supported with this accessory. It charged fine with my Docking station but now that has gone funny, used to be able to move the usb wire a bit and it charged but then went off, it hasn’t had water damage and obviously it is annoying now, ive booked a genius bar with Apple but Im wondering anything I can do ive cleaned the ports on my I phone as well