Hello - newbie to this forum, so I hope this is in the right place

I have an iPhone 3G (8GB), upgraded to ISO4. I want to link this to my TV, to watch iPad podcasts and YouTube.

Now, I also have a iPod Nano 3G. I can connect this to my TV using an Apple manufactured Composite AV Cable, and it works fine.

When I use the same cable to connect to the iPhone there is no playback whatsover (sound and video). The iPhone just plays as normal on its own screen. All the settings I can find in the iPhone in relation to 'TV Output' are turned on.

According to the Apple website here, this cable should be compatible with both devices.

Anyone know where I'm going wrong?