dvdauthor problem "chapter doesn't exist"

[ecc]

I was authoring a DVD and I got this error

ERR: Cannot jump to chapter 24 of title 1, only 23 exist
ERR: in VTSM pgc 5, button 6

Process aborted due to above error
Error code #6
There was an error in menu creation. One of the buttons jumps to a chapter that doesn't exist. Please review the log for more detailed information.

If the chapter doesn't exist, then why does it let me select it in the menu editor? I know the chapter exists because I picked the chapter timings by opening the m2v in Virtualdub using Avisynth and a d2v file to correctly index it. I went into the chapter timing menu in DVDAuthorGUI and counted the chapters. There are 24 (once again, I would not be able to choose Title 1, Chapter 24 in the menu editor if it didn't exist.

[borax]

Most probably this error is due to the fact that there is no I-Frame after the timecode for your chapter 24. Either remove chapter 24 completely or move it at least 1 second away from the current position (towards the beginning of the movie) and retry. Another problem could be the issue with drop frame/non drop frame timecodes and/or pulldown flags (these complicate the mapping between frames and timecodes).

[ecc]

Thanks, borax. You were right. It wasn't on an I-Frame. When I was figuring out the chaptering with Virtualdub (DVDAuthorGUI's preview decoder that gets the pulldown timings right takes too long to load the video), I first opened it as a directshowsource m2v and got a running time half the length it was supposed to be (probably because of the pulldown flag) so I opened it in DGIndex and generated a d2v and opened it as an mpeg2source with another Avisynth script file but that only gives you the K-frames (what virtualdub calls avi keyframes) and fortunately, that was the only chapter mark that was not on an I-frame. I opened the m2v file directly with virtualdub (which takes a lot longer to load up an m2v file) and picked a nearby I-frame for the chapter mark. I then ran the project again with success.