I have had the problem with digital disortion too when playing some tracks. I use Mediamonkey on XP, connected via USB to Young. Duffy: Rockferry, track 1 was one of the worst tracks.
I enabled volume control in Mediamonkey and turnrd down the volume to about 66%.
Now there is not any distortion at all and some other adwantages: The volume on my preamp is more equal to my other souces and I can control the volume via my iPod Touch (Monkeutunes).
Hope this can help...