[XeTeX] xparse fails

[Gareth Hughes]

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Dear fellow XeTeXnicians,

TeX Live updated a couple of times over the weekend, and a document that
compiled fine on Friday now fails. The document is not complex, and now
I see almost everything I've written is uncompilable. These documents
use fontspec, polyglossia, soul and hyperref, but I believe that it's
the fontspec call on xparse that creates the problem. Somewhere
something has changed.

The error message is
> (/opt/texlive/2009/texmf-dist/tex/latex/l3packages/xparse/xparse.sty 
> ! Undefined control sequence. <argument> \ExplFileName
> 
> l.57 ...e}{\ExplFileVersion}{\ExplFileDescription}

My XeTeX version is
> This is XeTeX, Version 3.1415926-2.3-0.9997.5 (TeX Live 2011)
> (format=xelatex 2011.7.20)  1 AUG 2011 23:18

The TLM tells me that I'm using revision 22347 (ver. SVN 2321) of xpackages.

Is anyone else experiencing problems? Can anyone sort this out for me?
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