iphone to car wont work

[crazy_e]

i have just got  new rca lead for my iphone 3g and it has 3 leads 2 audio and 1 video and it plugs in to my tv headunit fine no probs there but when i plug the phone it it says it is not compatible  so i disconected it from the car and conected it just to the phone and it still comes up with not compatable  so i pluged in my charger and it works fine any ideas?

[troublestarter]

which lead have you bough exactly? does it have a usb plug on it aswell?
do you have a pic of it
there are issues with iphones and these type of lead when the plug is connected and it is charging the video output will not work

[crazy_e]

it has the usb plug on it too i have not pluged in the usb part as it has no where to go on my setup

[crazy_e]

just to add the audio works great

[troublestarter]

i take it its not a genuine apple lead?

[crazy_e]

well i got it from the apple store in london and i dont have the box it came in but it does have the apple logo on it

is it something to do with the iphone softwear do you think?

[troublestarter]

it could well be what version are you running

[crazy_e]

4.1 i think just about to go to the latest version 4.2 tonight when i get home