printed bars thickness inconsistencies

[Jean-Alexis Montignies]

Hi All!

I have since I use lilypond some problems when printing. Bars (standard ones) 
are of different thickness.

It happens on my printer (Xerox 5400) but no on some others so I first thought 
it was a printer problem.

What makes me think it could be a problem with generated pdf is:
- it only happens with bars.
- it happens if I print with Preview.app (the display on the screen is correct) 
but not with acrobat reader (the print is correct with acrobat reader).
- the bars looks exactly the same wether I choose print definition of 300dpi or 
600dpi.

What do you think. How to check this? To dip into the generated postscript? (I 
think I'm not expert enough in postscript to pin point problems, may be some 
smoothing/rounding issue)

Greetings,

Jean-Alexis