QA: jsbook と multibib

【状況】
jsbook と multibib を組み合わせて使ってみたところ、文末のようなエラーが出ました。使用したソースは添付の test.tex で、そのまま enter で無理やり進めた後に dvipdfmx で変換したものが添付の test.pdf です。

「第 X 章」を出さなくするための行（20〜30 辺り）をコメントアウトした上で、jsbook を jbook に変更すると期待通りに動作します。「jsbook multibib」で Google 検索しても該当する問題は出てこないため、ここで質問させて頂きます。

jsbook や jsarticle だと再現しないため、BibTeX ファイルには問題ないと思います（添付しておりません）。

【質問】
jsbook と multibib の組み合わせで動作する場合、何か特殊な作業をする必要があるのでしょうか。もし簡単な作業で添付のソースを修正可能な場合は、どなたかご教示下さい。

【環境】
- OS X 10.6.5
- MacPorts から導入した、ptex（port install ptex +utf8）
- pTeX 3.141592-p3.1.10 (utf8.euc) (Web2C 7.5.4)
- dvipdfmx-20100328 by the DVIPDFMx project team

==========================
$ platex test
This is pTeX, Version 3.141592-p3.1.10 (utf8.euc) (Web2C 7.5.4)
(./test.tex
pLaTeX2e <2006/11/10>+0 (based on LaTeX2e <2003/12/01> patch level 0)
(/opt/local/share/texmf/ptex/platex/jsclasses/jsbook.cls
Document Class: jsbook 2010/03/14 okumura
) (/opt/local/share/texmf-dist/tex/latex/graphics/graphicx.sty
(/opt/local/share/texmf-dist/tex/latex/graphics/keyval.sty)
(/opt/local/share/texmf/tex/latex/graphics/dvipdfmx-contrib-latex/graphics.sty
(/opt/local/share/texmf-dist/tex/latex/graphics/trig.sty)
(/opt/local/share/texmf-dist/tex/latex/graphics/graphics.cfg)
(/opt/local/share/texmf-dist/tex/latex/dvipdfm/dvipdfm.def)))
(/opt/local/share/texmf-dist/tex/latex/hyperref/hyperref.sty
(/opt/local/share/texmf-dist/tex/latex/hyperref/pd1enc.def)
(/opt/local/share/texmf-dist/tex/latex/hyperref/hyperref.cfg)
Implicit mode ON; LaTeX internals redefined
(/opt/local/share/texmf/ptex/latex/url/url.sty))
*hyperref using default driver hdvips*
(/opt/local/share/texmf-dist/tex/latex/hyperref/hdvips.def
(/opt/local/share/texmf-dist/tex/latex/hyperref/pdfmark.def))
(/opt/local/share/texmf-dist/tex/latex/geometry/geometry.sty
(/opt/local/share/texmf-dist/tex/latex/geometry/geometry.cfg))
(/opt/local/share/texmf-dist/tex/latex/psnfss/times.sty)
(/opt/local/share/texmf-dist/tex/latex/subfigure/subfigure.sty
****************************************
* Local config file subfigure.cfg used *
****************************************
(/opt/local/share/texmf-dist/tex/latex/subfigure/subfigure.cfg))
(/opt/local/share/texmf-dist/tex/latex/amsmath/amsmath.sty
For additional information on amsmath, use the `?' option.
(/opt/local/share/texmf-dist/tex/latex/amsmath/amstext.sty
(/opt/local/share/texmf-dist/tex/latex/amsmath/amsgen.sty))
(/opt/local/share/texmf-dist/tex/latex/amsmath/amsbsy.sty)
(/opt/local/share/texmf-dist/tex/latex/amsmath/amsopn.sty))
(/opt/local/share/texmf-dist/tex/latex/amsfonts/amssymb.sty
(/opt/local/share/texmf-dist/tex/latex/amsfonts/amsfonts.sty))
(/opt/local/share/texmf-dist/tex/latex/tools/bm.sty)
(/opt/local/share/texmf/ptex/platex/otfstable/otf.sty
(/opt/local/share/texmf/ptex/platex/otfstable/ajmacros.sty))
(/opt/local/share/texmf-dist/tex/latex/multibib/multibib.sty) (./th.aux)
(./ra.aux) (./la.aux) (./cp.aux) (./co.aux) (./test.aux)
(I search kanjifont definition file: . . ) (I search font definition file: . .
. . . . . . ) (/opt/local/share/texmf-dist/tex/latex/psnfss/ot1ptm.fd)
(/opt/local/share/texmf-dist/tex/latex/hyperref/nameref.sty) (./test.out)
(./test.out)
1
(/opt/local/share/texmf-dist/tex/latex/psnfss/ot1phv.fd) [1] [2]
2
(./th.bbl [3] [4])
! Incomplete \ifx; all text was ignored after line 1.
<inserted text>
\fi
l.54 \bibliographyth{oxon}

?
! Extra }, or forgotten \endgroup.
\bibliographyth ... \refnameth \bibliography {#1}}

l.54 \bibliographyth{oxon}

?

! LaTeX Error: \begin{thebibliography} on input line 1\space ended by \end{docu
ment}.

See the LaTeX manual or LaTeX Companion for explanation.
Type H <return> for immediate help.
...

l.56 \end{document}

?
[5] )
(\end occurred inside a group at level 5)
(\end occurred when \ifx on line 1 was incomplete)
(\end occurred when \ifx on line 1 was incomplete)
(\end occurred when \iffalse on line 1 was incomplete)
(\end occurred when \iffalse on line 1 was incomplete)
(\end occurred when \ifx on line 1 was incomplete)
(\end occurred when \ifx on line 1 was incomplete)
(\end occurred when \ifnum on line 1 was incomplete)
(\end occurred when \ifx on line 1 was incomplete)
(\end occurred when \ifnum on line 1 was incomplete)
(\end occurred when \iftrue on line 1 was incomplete)
(\end occurred when \ifx on line 1 was incomplete)
Output written on test.dvi (5 pages, 4488 bytes).
Transcript written on test.log.

test.tex