Problem with last miktex update

Hi all,

this morning I've updated miktex and now I cannot use beamer with siunitx  
(both packages updated today).

Processing
%----------------
\documentclass{beamer}
\usepackage{siunitx}
\begin{document}
\begin{frame}{First}
\end{frame}
\end{document}
%-------------------
  fails showing next message

Package: siunitx 2012/11/13 v2.5k A comprehensive (SI) units package


! Use of \@pr@videpackage doesn't match its definition.
\beamer@ifnextcharospec #1#2->\def \reserved@a {
                                                 #1}\def \reserved@b  
{#2}\fut...
l.29   }

? x

I don't know if the problem is with CTAN package versions or MikTeX  
versions, and I don't know
what to do to go back to a useful situation. Yesterday everything worked.

Could you help me?

Thank you,

Ignasi

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