Hi,
\underbrace is doing strange things. Minimal example:
\documentclass{minimal}
\usepackage{fontspec}
\usepackage{unicode-math}
\setmainfont{TeX Gyre Pagella}
\setmathfont{Asana Math}
\begin{document}
\[\underbrace{123}_{456}\]
\end{document}
Why is that and how to help?
ciao
Toscho