I experienced this same error (Internal Software Error: .\Vobulator\TitlePlanner\CGOPGrouper.cpp, line 297) and thanks to your link I was able to resolve my issue at least.
Considering there is not a lot of info about this error out there, I thought I would share my resolution and hopefully save other 5 hours of endless searching.. :-/
On the other thread:
Jeff Bellune states “The next culprit to check would be Chapter Playlists. Do you have any, and if so, how many? More than 19 from a single timeline can generate this error.”
In my case I had exactly 19 chapter markers on my Timeline and by removing the last one I was finally able to build the DVD. Apparently Encore adds a “hidden chapter point” at the end of the timeline.. Which in my case would make it more than 19… Though not visible, it did cause an issue and my build was failing.
It would nice if Adobe provided patches for these non issues. They are obviously BUGS and need to be addressed!!