rectangle instead of a square

Hello VisAD users

I hope there is some place for another 'newbie' question:

I want to display an image using DisplayJ2D and Integer2DSet. The image is
represented by the simple function ((rows,columns) --> whereby the X- and
the Y-Axis have the same range.

It works fine on the NT machine with a 17" display. But on my working
place (Solaris, 21" monitor) the image (and the pixel)  will be displayed
as a rectangle and not as a square. I've tested  the 'setRange' and the
'setAspect' method but nothing changes.

Maybe this problem has to do with the screen resolution,but I'm not sure.