Hi Joe,
I found a private tracker entry originated from you, describing a very similar problem. It is currently scheduled to 6.4.01, and most likely is the result of some email conversations, as I didn't find any reference to a forum thread. I did attach your new sample project to that entry and I also made a note there to comment on this forum thread when it is fixed. You are welcome to inquiry about it as VWG-7919.
A developer did take a quick look at that sample help file and made a comment that the attached CHM file did not contain #TOCIDX, and that we need to fix our code to handle that case. Don't know if it helps you knowing that, but the best I can do at the moment.
Hope this helps,
Palli