Problem with beamer's \pause in alignments

Anonymous created an issue

The following code

\documentclass{beamer}
\mode<presentation> { \setbeamercovered{transparent} }

\begin{document}
\begin{frame}
$\begin{cases} v(t,x) &= g(t,x), \\ \pause u(x) &= f(x) \end{cases}$
\end{frame}
\end{document}


compiles nicely, but everything except "u(x)" already shows up on the first slide if I use beamer.cls v 1.70 2007/03/11 18:50:44. With v 1.55 2004/10/11 16:09:50 everything works as expected: On the first slide, the full second line is shown in transparent style. This seems similar to issue #87.

The same happens if I use plain TeX's \halign, so cases is not the culprit. Moreover, if I don't use \setbeamercovered{transparent}, then everything works as expected. In other words, \pause doesn't work together with \setbeamercovered{transparent} and \halign.

I've also posted the issue here: http://tex.stackexchange.com/q/6348/1235

1. This is due to the way cases is implemented, and without major changes to both beamer and amsmath it's not going to change. It's therefore a 'known issue' (and is covered in the manual).