[pstricks] Problem with YAP previewer

[Blair Hall]

I have trouble visualising node diagram labels with the YAP previewer
(YAP 0.98n 2001). If I write

     \begin{psmatrix}
       E&F\\
       G&H
       \ncline{1,1}{1,2}^w
       \ncline{2,1}{2,2}_f
       \ncline{1,1}{2,1}<u
       \ncline{1,2}{2,2}>v
     \end{psmatrix}

The w,f,u and v labels are all drawn in a pile covering, but
slightly to the right of, the node label H.

I thought it was my installation for a while, until I checked by
running dvips to get a PostScript output. In THAT case, the
labels are all as they should be!

Is this a known problem with YAP? Can I fix it?

Many thanks

Blair