When you view the page in IE (I use IE7), then thumbnails are at the top, where they belong. When you view it in Firefox (I use Firefox 3), the images are at the bottom.
I've changed the padding and margins -- does not resolve it.
I've looked in the CSS for the "max-width:100%" and neither my template CSS nor the NextGen gallery has this.
I have no idea what could cause this. Any thoughts?