hi all, just need a little bit of help,

i've connected my Macbook Pro to my Humax tv via. some funky cable and i can see my desktop image On the tv on no icons or anything.. the main reason for this is clearly just to watch DVDs and programs i have on my mac however upon opening VLC player into fullscreen or Front Row the screen will misleadingly go black as if about to play something but the media will only play through the mac!?

any help would be hugely appreciated, i'm not sure if i need to change some settings somewhere or not..

thanks in advance..