I'm sure this is an obvious fix but I cant figure it out.

I've installed mythbuntu on my P1AH2 system with a NOVA-T 500 DVB-T tuner card.  The card is registered by the kernel and after activating the low noise amplifier I can tune all the freeview channels in New Zealand.  The strange thing is when I watch TV I can only get audio on TV3 (which incidentally looks amazing in 1080i).  I can see all the other channels but I can’t hear them.

It’s my understanding that TV3 broadcasts using H.264 video with the AAC audio codec whereas other channels use something else for audio MP2?  Perhaps someone else has encountered and fixed this problem..