[XeTeX] strange xelatex behaviour, possibly bug?

[Arnošt Štědrý]

hi all,

i found strange problem with the xelatex.

compiling this minimal example:

\documentclass[twoside]{book}
\usepackage{fontspec}
\usepackage{xunicode}
\usepackage{xltxtra}
\setromanfont[Mapping=tex-text]{Minion Pro}
\begin{document}
2008\_07-08
\end{document}

xelatex produce this result:

2008_07-07-08

i use xetex 996:

xetex -version
XeTeX using libpoppler 3.141592-0.996 (Web2C 7.5.6)
kpathsea version 3.5.6
Copyright 2007 SIL International.
Kpathsea is copyright 2007 Karl Berry and Olaf Weber.
There is NO warranty.  Redistribution of this software is
covered by the terms of both the XeTeX using libpoppler copyright and
the Lesser GNU General Public License.
For more information about these matters, see the file
named COPYING and the XeTeX using libpoppler source.
Primary author of XeTeX using libpoppler: Jonathan Kew.
Kpathsea written by Karl Berry, Olaf Weber, and others.

Compiled with ICU version 3.4 [with modifications for XeTeX]
Compiled with zlib version 1.2.3; using 1.2.3
Compiled with FreeType2 version 2.3.5; using 2.3.5
Compiled with fontconfig version 2.4.2; using 2.4.2
Compiled with libpng version 1.2.26; using 1.2.26
Compiled with libpoppler (xpdf version 3.00)

-- 
Arnost Stedry