[XeTeX] Linux Libertine font problem

[Mehdi Omidali]

Sorry if it is not related to this list. I tried to use the latest
release of the Linux Libertine font with xelatex on Miktex 2.7
(everything is in its latest version). I compiled the following lines

\documentclass{article}
\usepackage{fontspec}
\setmainfont{Linux Libertine O}
\begin{document}
Th \textit{Th}
\end{document}

and I got  an incorrect character for \textit{Th}. Again when I
replaced "Linux Libertine O" with "Linux Libertine", I got a normal
"Th" for \textit{Th} which should be in italic but it wasn't.
Thanks