How to make a series of step-by-step figures has a fixed position on every beamer frame?

Question

Some frames have texts describing steps on the associated figure. I want to make the figures still fixed in position no matter there is a description text.

\documentclass{beamer}
\setbeamertemplate{navigation symbols}{}

\usepackage{pst-eucl}
\psset{PointName=none,PointSymbol=none}
\newpsstyle{helper}{linewidth=.5\pslinewidth,linecolor=red,arcsep=-1}

\begin{document}
\begin{frame}{Problem No. 2}
\only<1>{Draw the $x$ axis.}
\only<2>{Draw a line at angle $45^\circ$.}
\only<3>{Draw an arc of radius 2 intersecting both lines.}
\begin{pspicture}[showgrid=false](-5,-1)(7,5)
    \pnodes(0,0){O}(5,0){X}(4;30){A'}
    % x-axis
    \only<1->
    {
        \psline(X)
        \uput[-135](O){$O$}
        \uput[-45](X){$X$}
    }
    % vector A
    \only<2-4>{\psline[style=helper](A')}
    \pstInterLC[Radius=\pstDistVal{2}]{O}{X}{O}{}{I1}{I2}
    \pstInterLC[Radius=\pstDistVal{2}]{O}{A'}{O}{}{J1}{J2}
    \only<3-4>{\pstArcOAB[style=helper]{O}{I2}{J2}}
    \only<4-5>{\psline{->}(O)(J2)}
    \only<5->{\uput[90](J2){$A$}}
\end{pspicture}
\end{frame}
\end{document}

As you can see from the following animation, the current result shows the figures move up and down. How to fix it?