Yep, I have that problem with one particular gallery. All of the images have a white border, but it doesn't show when viewing the gallery page. if you click on an image, it will load and have a very faint line depicting where the edge of the image border is. As it is now, the images on the gallery page look small due to not being able to tell where the edge of the white borders are.
http://fineartamerica.com/profiles/greg-jackson.html?tab=artworkgalleries&artworkgalleryid=367149
I added a disclaimer of sorts within the gallery description above the imgaes, but there's nothing to guarantee a customer will read it.