I have one UK HD-DVD myself (Planet Earth) and this one also plays without problems on my machine.
Some things came into my mind which you maybe can test. What happens if you don't apply the Nav chain bugfix but zero the CPI field, does this solve your problem too? And what happens if you, after the playback problems are gone, seek back to eg. the beginning of the movie where you had these problems, are they still gone or do they reappear? Whats happens if you don't play the movie from the beginning but start at a higher chapter?
