[pstricks] opaque boxes

[Andrew Olenko]

I am trying to create tree in Latex with pstricks (see ТеХ file below, 
and ps here http://www.mechmat.univ.kiev.ua/probability/temp/Tree.ps)
But some \psshadowbox are limpid (I can see lines under it), and some 
other not. How I can make opaque boxes?
Many thanks in advance
Andrew Olenko
================
\documentclass[legalpaper,11pt]{article}
\usepackage{pstricks} % To use the standard "color" package with PSTricks
\usepackage{pst-tree}
\usepackage[cp1251]{inputenc}
\usepackage[english,ukrainian]{babel}

% New colors
\definecolor{LemonChiffon}{rgb}{1,0.98,0.8}
\definecolor{ForestGreen}{rgb}{0.13,0.55,0.13}

\newcommand{\MyNode}[2]{%
\Tr{\psshadowbox[fillstyle=solid,fillcolor=#1]{\tiny #2}}}
\newcommand{\NoeudXt}[1]{\MyNode{LemonChiffon}{#1}}
\newcommand{\NoeudMotif}[1]{\MyNode{white}{\textcolor{black}{#1}}}

\psset{armA=5mm,armB=5mm,angleA=60,angleB=-60,levelsep=2cm,treesep=5mm}

\pagestyle{empty}

\begin{document}
\begin{center}
\begin{pspicture}(-8,-14.5)(8,1)
\rput(-2,-6){%
\pstree[treemode=R,treesep=\baselineskip,levelsep=*2.5mm,nodesep=1mm,
xbbd=0.2,linewidth=0.15mm]{\Toval{aaaaaaaaaaaaaaaa}}
{\pstree{\NoeudXt{aaaaaaaaaaaaaaaa}}
{\pstree{\NoeudMotif{aaaaaaaaaaaaaaaa}}
{}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}}
\NoeudXt{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudXt{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudXt{aaaaaaaaaaaaaaaa}
\NoeudMotif{aaaaaaaaaaaaaaaa}
\NoeudXt{aaaaaaaaaaaaaaaa}
\NoeudXt{aaaaaaaaaaaaaaaa}}}

\end{pspicture}
\end{center}

\end{document}