powersem broken after automatic package maintenance

I have used powersem for long. Today I tried to run a set of old slides and MikTeX automatically updated (loaded a set of files related to seminar).
I could not get powersem to work. It seems that powersem is broken. Here you have a minimal example and the error that it generates.

\documentclass{powersem}
\begin{document}
%-------------------------------------------
\begin{slide}
\textbf{Texpower is not working any longer}

Hello, Hello
\end{slide}
%-------------------------------------------
\end{document}

("C:\Program Files\MiKTeX 2.9\tex\latex\seminar\seminar.bg2"
seminar.bg2: various corrections for the Seminar document class
added since seminar.bug and few add-ons for overlays
(Version 2.3 of <2014/05/12> (DG, hv))

! LaTeX Error: Command \SeminarNextOverlay already defined.
               Or name \end... illegal, see p.192 of the manual.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
...

l.591 ...{overlay}{\the\c@overlay}#1\end{overlay}}

?

Thank you for your help.

Luis A. Escobar
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