The PNG image is fine, as shown here


Any idea as to what is causing this? The image that is corrupting is a white fill marker, all my other colours for the same marker are perfectly fine. I thought at first it was due to being a pure white colour (#FFFFFF) so I did try a ever so slightly off white colour (#FEFEFE) but to no avail.
ps, the image isn't quite true of a DC10/MD11 yet, but I don't want to put further work into making it exact if all the markers aren't going to display well, especially as most the markers are going to display as the corrupted image.