[XeTeX] Fonts and Snow Leopard

[James Townshend]

Hello,
I'm a relative novice in the field.
Since updating to 10.6 my starting code for most documents
		 %!TEX encoding = UTF-8 Unicode
		 % !TEX TS-program = XeLaTeX-xdv2pdf
		\usepackage{fontspec,xunicode,xltxtra}
		\setmainfont{Helvetica Neue Light}
only produces text in pdf in helvetica. Switching to a serif font,  
still produces the same result.
I reinstalled MacTeX2008 but the issue remains.
Does anyone have any suggestions?
Many thanks,
James Townshend