Image aspect ratio not maintained in NGG slide show

Greetings from a Newbie. I am Webmaster for a new site built with WP 3.0.4 and BuddyPress, with NGG for image gallery presentation. NGG works fine, but for a problem:

When I create a gallery with jpg images of varying sizes, from 150 x 150 to 640 x 480, and a few 800 x 600, the smaller images appear to be constrained horizontally from the right when they show in the Slide Show mode. In these instances, the aspect ratio is not maintained, and the image is compressed horizontally. These same images have normal aspect ratio in the Individual Picture mode.

Option setting for Resize Image = 800 x 600.

Option setting for Slideshow is Default Size = 640 x 480. If I reduce this to 480 x 360, the aspect ratio problem is diminished. With 320 x 240, it disappears, but the slideshow image size is too small for our use. I’d like to use 640 x 480. How can I do that without the loss of aspect ratio?

Thanks, Airpilot