Click wheel ipod (A1199) will not work in new Ford Foucs 2011.

I've just got a new Ford Focus which has the line in and usb connections for the ipod. The line in works fine. The usb doesn't quite work though. The ipod is recognised by the car and all the tracks are listed etc and I can control what I want to do with the steering or manual controls of the car but there isn't any sound? I'm using the cable that came with my ipod (both work fine, although the ipod is an old Nano A1199 type - not sure what gen this makes it). Checked for updates and the apprently the ipod is up to date. Does anyone have any suggestions bar having to get a newer ipod or is it just due to the fact that it's an old ipod and I'll just have to use the line in function. thanks