Do you get thin lines on the edges of the images? Thinner than 1px?
If so, it seems to be related to the way the browser scales images when zooming. It seems to take some data from the next line in the image, and use that as a part in the image interpolation.
I solved it by adding 1 line of background-colored pixels to the image. Not ideal, I know, but it was the only solution I found that worked.
