[pstricks] nodes and FP package

[Francisco A. S. Grossi]

I have an strange behavior that I cannot figure out. I draw two nodes and 
connect them:

- with direct definitions
- with coordnates calculated by FP package

The results slhoud be identical, but they are displaced relative to each 
other. The example with FP package is displaced to the right, as the small 
sample shows.

I need FP because I am coding a command top draw a network of nodes and 
their coodinates must be calculated through a copule of parameters.

Any ideas?

 \documentclass[a4paper,12pt,fleqn]{article}
 \usepackage[T1]{fontenc}
 \usepackage[brazil]{babel}
 \usepackage{pst-all}
 \usepackage[nomessages]{fp}

 \begin{document}

 \begin{pspicture}[showgrid=true](0,0)(10,5)
  \FPsub\xp{4}{0.8}
  \FPadd\yp{0}{1.0}
  \cnode(\xp,\yp){0.2}{1e}
  \FPadd\xp{4}{5.3}
  \cnode(\xp,\yp){0.2}{1s}
  \ncdiag[angleA=90,angleB=90,arm=1.5cm]{->}{1s}{1e}
 \end{pspicture}

 \begin{pspicture}[showgrid=true](0,0)(10,5)
  \cnode(3.2,1){0.2}{2e}
  \cnode(9.3,1){0.2}{2s}
  \ncdiag[angleA=90,angleB=90,arm=1.5cm]{->}{2s}{2e}
 \end{pspicture}

 \end{document}