I have started to use an enterprise specific class for LaTeX, but have got a problem with usage system fonts in Ubuntu. The class uses the fontspec package, I have therefore been instructed to use XeTeX (i.e. the command xelatex instead of latex or pdflatex). However, the command xelatex testfile.tex results in the following message:

! Package xkeyval Error: `TeX' undefined in families `Ligatures'.

See the xkeyval package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.61 \newfontfamily\headfont{Arial}

? 

The class has previously been used on Mac and Windows and the font setup is as follows:

\newfontfamily\headfont{Arial}
\newcommand\texthead[1]{\headfont #1}
\setromanfont{Georgia}
\setmainfont{Georgia}
\setsansfont[Scale=MatchLowercase]{Verdana}

It has been suggested that since XeTeX makes use of system fonts and the class file has worked flawlessly on Mac and Windows, the problem might be that Arial is not a name used in Ubuntu. I have tried to exchange Arial with Ubuntu Light in the setup code above, but that have not been any improvement.

Any suggestions please on how to move forward?