[Plugin: NextGEN Gallery] "up-size" the images

When I use the nextGEN galleri the picture are up-size to the set resize pixel height and width. The picture I uploaded had a size who was smaller (400pixesl i width) then 640×640 pixels that I have set in options for the Images. When I click on the picture i my website, the picture is shown with 640 pixels, not 400pixels as the uploaded original.
Then the picture is destroyd in showing and not pretty to look at.

I use WP 3.0.1, and plugin nextGEN 1.6.1 and I also use plugin nextGEN resize versjon 1.3b and both plugins are set to 640 pixels width