[XeTeX] bug using \underbrace with unicode-math package

[Daniel Greenhoe]

Using \underbrace with the unicode-math package under XeLaTeX produces
garbage output. Here is a minimal example:

\documentclass{book}
 \usepackage{unicode-math}
 \setmathfont{xits-math.otf}
\begin{document}%
 \[ \underbrace{xyz} \]
\end{document}%

Using the mathspec package instead of unicode-math seems to be OK.
The \underbrace with unicode-math problem was discussed almost one year ago.
Does anyone have a solution?

I posted an email very similar to this one more than 48 hours ago but
received no responses. My previous post included a web link and I fear
this may have caused the email to be identified as spam. This email is
basically a repost. If you received the previous email, I apologize
for the annoyance.

Dan