[XeTeX] Can't find xetex.xfmt...

[cormullion]

I’ve been following the instructions for installing Xetex on the web site. I’ve downloaded Core TEX, XeTex, and TexShop. This is my first error message when I click the Typeset button in TexShop. I’d be very grateful if someone could suggest a few diagnostic tactics...

> This is XeTeX, Version 3.14159-2.1-0.88 (Web2C 7.5.2)
> kpathsea: Running mktexfmt xetex.xfmt
> fmtutil: no info for format `xetex'.
> I can't find the format file `xetex.xfmt'!

thanks