Derrow is away on business for a week or so. It sounds to me like you have a movie with non-seamless branching in it, and it has (at least) 2 alternate versions of chapter 20. BTW - everybody - the next and previous buttons DO NOT cycle through the chapters. They move forward or backward through the PROGRAMS. Usually this is the same thing, but not necessarily. A chapter can have more than one program (and a program can have more than one cell). AND the navigation features of the Virtual Machine are not restricted to menues (e.g. the White Rabbit in The Matrix). Once into an ILVU the pointers within the NAV pack (there are 2 sets, one for seamless, the other for "non-seamless") guide the playback. So, in summary, it is possible to have a program in a PGC which is skipped during normal playback because it is interleaved with the program which does play.