Compilation fails with eqnarray after reinstalling Miktex

I have a script that extracts math formulae from a tex file, produces a
small standalone file for each formula and compiles it with pdflatex. The
standalone pdf files are then used to produce png images of the formulae.
The script has always worked smoothly with Miktex 2.8 under windows Vista.
Now that I have updated to version 2.9 and Windows 7, it does not work any
longer. Every time it encounters an eqnarray environment, it gives the
following error:

 ! Missing \endgroup inserted.
<inserted text>
                \endgroup
l.6 \begin{eqnarray}

For example, I get this error when I run pdflatex on the following simple
file:

\documentclass[12pt]{standalone}

\begin{document}

\begin{eqnarray}

1&=&1\\
1&=&1

\end{eqnarray}

\end{document}

Why am I getting this error? Has support for eqnarray been discontinued in
new versions of Miktex?

Thanks for any help you might provide.
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