[XeTeX] Problem displaying Chinese font with \netfontfamily

[Haines Brown]

I'm migrating from LaTeX to XeLaTeX on Debian Squeeze with TL2100, 
but having trouble with XeLaTeX display of Chinese characters:

    \documentclass[12pt]{article}
    \usepackage{xltxtra}
    \setmainfont[Mapping=tex-text]{Linux Libertine O}
    \usepackage{xeCJK}
    \setCJKmainfont{AR PL KaitiM GB}
    \newfontfamily\sungtiGB{AR PL SungtiL GB}

    \begin{document}

        Main font: 无为

        Sung font: {\sungtiGB 无为}

    \end{document}

The chinese characters are all displayed with main font "AR PL KaitiM 
GB" but the \newfontfamily only displays the main font, not the font
it specifies. But if I set "AR PL SungtiL GB" at main font, it displays
properly.

Haines Brown