This sounds pretty similar to an issue that I am
experiencing.
Basically in IE5 on Windows 2000, IE6 and IE7 on Windows XP,
the table of contents appear as required - all books are not
expanded, and once the user clicks on a book, the book is expanded.
However in IE7 in Windows Vista and in Firefox on all Windows
platforms, the table of contents appears with all books expanded,
and when clicking on a book, the book will not collapse.
However if the same page is directly navigated to (e.g.
http://servername.com/dir1/index.htm)
the table of contents appears correctly (all books collapsed and
users able to expand and collapse a book by clicking on it).