wxHtmlHelp: no item tree

wxPython Users
1

trying wxHtmlHelpController (2.6.1.0,XP):
In the left window is no tree from the hhc-file only the book title
(but the item to display via .Display is corectly shown).
Worked with 2.2.2

hhp-file:
  Contents file=abc.hhc
  Index file=abc.hhc
  Title=book
  Default topic=abc.html

abc.hhc has the following form:
<A name="book"></A>
<body>
<ul>
  <li><object>
        <param name="Name" value="chapter 1">
        <param name="Local" value="abc.html#chap1">
      </object>

  <ul>
    <li><object>
          <param name="Name" value="chapter 1.1">
          <param name="Local" value="abc.html#chap1.1">
...

Udo