I was getting weird audio stuttering and freezes during LMCE playing *some* recorded HDTV programs. These would play fine using Mythtv or normal Xine, so I knew it was not hardware or the linux or alsa configs.
Anyway, I had to change /etc/pluto/xine.conf line from
audio.alsa_front_device:plughw:0
to
audio.alsa_front_device:default
This cured the problem.