Anyone work much with lightbox.js?

Hello everyone-

I am having a problem when using lightbox to display some thumbnails. Upon opening the first image as the bounding box streches verticaly a black bar appears at the bottom of the box just as it is reaching it’s full height, it soon vanishes, but for a split second the entire width of the screen is spaned by a small black bar.

This never happens when resizing an already open set of images, but only on the initial open.

Has anyone incountered this before or know what may be causing it?