[Qgis-user] strange border plot

[flavio rigolon]

Hi all,
 I'm trying to plot (both on PDF and printer) a simple
layout with polygons wich style is quite symple: no fill and black
border (width 0,10 mm).

The result is: the polygon are rendered with a "various"
width border. Start quite fine and end quite large...

An example here: http://dl.dropbox.com/u/1542005/qgis_border_test.png

I obtain it both on debian testing and windows 7 prof (64 bit) with QGIS 1.6

What's wrong?
thank in advance for any hint?
flavio