Mini displayport adapter to HDMI problems

Hi
I just bought a mini displayport to hdmi adapter (with sound) - its a kanex model.

Excitedly, I plugged in and connected the hdmi lead to the TV. Nothing has indicated that there is another display attached. I've clicked "detect displays" but it doesn't find anything. The LED on the adapter does not light up either.

The TV is on, I've verified that the hdmi cable works and that the ports on the TV are working by connecting other devices.

Have I received a duff displayport adapter or am I doing something wrong?

I have a macbook pro running snowleopard. The TV is a Sony Bravia KDL 32W5810

Thanks

Zig


PS if this is the wrong forum, please let me know where I need to go...