[hubblec4]

It was easy to find the issue.

ChapterGrabber's XML files do not correctly use the matroskachapters.dtd match.

There are no UIDs for the editions or the chapters, but this are mandatory elements.
The timecodes are not correctly too (but works).
CG-xml

<?xml version="1.0" encoding="utf-8"?>
<Chapters>
  <EditionEntry>
    <EditionFlagHidden>0</EditionFlagHidden>
    <EditionFlagDefault>0</EditionFlagDefault>
    <ChapterAtom>
      <ChapterDisplay>
        <ChapterString>Prologue</ChapterString>
        <ChapterLanguage>eng</ChapterLanguage>
      </ChapterDisplay>
      <ChapterTimeStart>00:00:00</ChapterTimeStart>
      <ChapterFlagHidden>0</ChapterFlagHidden>
      <ChapterFlagEnabled>1</ChapterFlagEnabled>
    </ChapterAtom>
....

Mosu's chapter editor generate this UIDs automaticly.
i could make that too in cE.

EDIT:

Originally Posted by von Suppé

...
In the past chapterEditor accepted these xml outputs - for editing - without a problem.
...

since rev0.02 is the XML-valid-procedure not changed.