Hi Claes.
Thank you for your quick answer.
Are you working on two machines, two monitors and two graphic cards, or…?
Yes, i do 
Which ICC profile is marked as (default)?
There are two profiles in the list, sRGB and the one for my monitor SL27T-1 LED (fujitsu).
None is marked as default, and the button to do so is grayed. (i will fix that tomorrow)
But: I have produced the images on the different machines, yes, but i examined them on the windows-machine side by side, then both on the linux-machine. They look different in spite of the same pp3-profile.
You can see the two images here (open them in separat browser-tabs and compare):
http://www.coonlight.de/fotos/cat-manual-windows.jpg
and
http://www.coonlight.de/fotos/cat-manual-linux.jpg
As i know the monitor-icc should not affect the images themselves.
Best regards
Peter