[pstricks] problem with tree with LARGE nodes

[Hendrik]

Hi,
I'm using avm.sty (to be found at http://tinyurl.com/66enx) to produce 
boxes like this:

\newbox\DP
\setbox\DP=\hbox{\begin{avm}
                                    \[\emph{phrase}\\
                                        head & \@4\[\emph{noun}\\
                                                                agr & \@2
                                                                \]\\
                                        val & \[\emph{val-cat}\\
                                                        comps & itr\\
                                                        spr & $+$
                                                    \]
                                    \]
                                \end{avm}}

and I want to use them inside \pstree like this:

\newpsobject{knoop}{TR}{ref=b}
\psset{nodesep=3pt, levelsep=7ex}
\pstree{\knoop{\box\DP}}{
   \pstree{\knoop{\box\DP}}{
        \pstree{\knoop{\box\DP}}{
             \knoop{The}
        }
    }
}

This works fine as far as the production of the avm's is concerned, but 
inside the tree they all overlap.  It is as if pstricks thinks the nodes 
are dimensionless. 

This is a working minimal example. Note how the two avms are put on top 
of each other.

How can I solve this?

Thanks, Hendrik

-- 
Hendrik Maryns
Rijakker 29
9030 Mariakerke
België
+3292277178