Stevek trust me I'm having the same issue. For example. The dark knight loads fine but when you select in the settings hd bitstream it crashes back to the main powerdvd screen still in 23 hz refresh mode. Which then have to manually change the refresh rate in nvidia drivers menu then completely close and restart powerdvd. It also fails on the current Star Trek movie.
What's really annoying is once you figure out how you get the hd bitstreaming on, hitting the next or previous chapters button also crashes the movie back to power DVD main menu.
It only works on some movies.
It's always like one this gets fixed and then they break something else in the patch. I'm getting annoyed. Can sit and truly enjoy the movie experience.