adding hebrew breaks table of contents???

[Eitan Suez]

hello,

  i maintain a document that i wrote using lyx.
  recently i added some content that uses a mix
  of two alphabets:  english (primary language of
  the document) and hebrew.

  now when i export the document to pdf
  (with lyx --export pdf2 guide.lyx)
  i notice that the table of contents is messed
  up.  specifically, the chapters hierarchy ends up
  nested somehow.  instead of 1-2 dozen chapters,
  i see only chapters 1 & 2, where ch3 is nested as
  a child element inside chapter 2.  this repeats
  so that for example chapter 7 is inside chapter 3.
  so the whole toc is output, but the hierachy is
  messed up.

  the text changes i made to my lyx file are nowhere
  near the table of contents so i have no clue why
  this mixed language text addition should cause this
  problem.

  here is the diff between a working lyx file and one
  that produces the messed up toc:

 \begin_layout LyX-Code
-InternalFrame.closeButtonToolTip=
+InternalFrame.closeButtonToolTip=
+\lang hebrew
+סגור
 \end_layout

 \begin_layout LyX-Code
-InternalFrame.iconButtonToolTip=
+InternalFrame.iconButtonToolTip=
+\lang hebrew
+הקטן
 \end_layout

 \begin_layout LyX-Code
-InternalFrame.restoreButtonToolTip=
+InternalFrame.restoreButtonToolTip=
+\lang hebrew
+החזר
 \end_layout

 \begin_layout LyX-Code
-InternalFrame.maxButtonToolTip=
+InternalFrame.maxButtonToolTip=
+\lang hebrew
+הגדל
 \end_layout

 \begin_layout Section


any help would be greatly appreciated.  i have already tried
to just output the hebrew without the enclosing \lang tag but
that causes an error in the export.

thanks,
/ eitan