I have my Pioneer 4280XD connected to a Panasonic BDP30 Bluray player via HDMI, using the Pioneer's own speakers. When watching some DVDs, I have noticed the sound is sometimes out of sync with the picture (the soundtrack is slightly ahead). It is noticeable enough to be annoying, but it does not occur constantly, and tends to develop through the course of the film. Does anyone have any suggestions as to what might be causing this problem, and how I might rectify it? Many thanks for any suggestions.