No TV out on iPod Touch 4G using Apple Composite AV Cable
I have an iPod Touch 4G, and want to connect it to my TV. I bought the correct Apple Composite AV Cable as shown on the Apple website. When I connect it up, I get audio through the TV but no video. I have tried my old iPod classic and my wifes iPhone 3Gs, and they both play perfectly. Have I missed something? I'm led to believe that I don't have to alter any settings in the Touch, it should be 'plug & play'. Any help that you could give would be gratefully accepted - it's American Football season, and I have Sky Mobile!
iPod touch, iOS 4.2