Blue & Me and iphone 3gs

Can anyone help, I've got the fiat 500 with blue and me and an Iphone 3gs. The phone is paired perfectly with the car and phonecalls all work. I also connect it with the blue & me adapter to the USB for music. This works the first time I attach it but if I stop the car and try again it does not recognise the media. The wierd thing is if I wait 24 hours it will work again, but ONCE only!! Very annoying, I'm having to plan which stage of a journey will be the longest in order to get the maximum listen! Please help...