Problem mixing portrait and landscape images

This might be a problem more with dewslider.swf than diaporama, but diaporama exhibits the problem:

Attempting to create a slideshow from an image gallery that has images which are both portrait and landscape orientations (i.e 640x480 and 480x640 images) does not display correctly. If the first image is a landscape, subsequent portrait images will be stretched to the wider landscape width. If the first image is a portrait, subsequent landscape images overlay, but are not completely erased when another portrait image is displayed (i.e a sequence portrait, landscape, portrait shows the problem). What should happen in both cases is that the background is erased before drawing, and images should not be stretched.