I have no problem playing back converted DVD's using mediaconverter (same parameters as Martin: 400x240, 512, 64) and playing with UKMP. Just now tried it again - very smooth, excellent quality. There have been times when I began watching and there were occasional glitches. I found that when I switched the n800 to offline mode, the glitches disappeared. As I recall, this usually occurred when I was out of wireless contact so it may have been related to the n800 periodically trying to establish wireless contact.