Anyone know what is up with the sound on MTV on Sky Digital?

When I watch this channel through my home theatre amp in Pro-Logic II mode, the voices that would normally come through the centre speaker come through rear and front left and right speakers, so that the sound of the voice is all around you. I know it is not my amp as other channels do not do this. It even sounds slightly tinny or echo-y on my little mono portable TV in the bedroom.

I am wondering whether Sky or MTV have put some kind of filter over the audio of their channel with the intention of 'enhancing' music, but to the detriment of normal speech (and lets face it, music is hardly a feature on MTV these days!)

Steve