[pstricks] problem in equation numbering

[Kari Eloranta]

This might not be a pstricks related question, but any help is greatly appreciated. I have created a macro

\newcommand{\info}[1]{%
\vskip10pt
\noindent\psframebox*[framesep=10pt,% 
 fillstyle=solid,%
 fillcolor=yellow!55,% 
 linecolor=black]{\parbox[c][\height][s]{\textwidth-18pt}
{\noindent  #1}}
}

which draws a filled yellow box around #1. If I call the macro with

\info{{\blue Resistance}\\%
The resistance of an electrical component is
\begin{equation}
R=\frac{V}{I}
\end{equation}\label{eq:res} 
where $V$ is the potential difference across the component, and $I$ the electric current flowing through it.}

the equation number (label) becomes 1.20 in the output pdf. However, when I try use \ref{eq:res} to reference the equation, the reference tag is 1.10 instead of 1.20. Recompiling does not help. Is there a solution to this problem?

Best regards,
  Kari