Your gallery's dimensions are square (it is loaded into a 960px x 960px iframe) but with thumbnails to the left or right of the main image, your gallery's image area will be rectangular in shape and portrait-style, better suited to displaying portrait images than landscape. As long as your images are large enough and imageScaleMode is set to SCALE or SCALE_UP, then your landscape images will still be displayed as large as possible within the image area. For them to be displayed any larger, cropping would have to occur.
Possible solutions to your problem:
(1) Check that your gallery's maxImageWidth and maxImageHeight are not set too low.
(2) If using imageScaleMode="SCALE", make sure that your main images are large enough that they would need to be scaled down to fit within the image area. Otherwise, set imageScaleMode="SCALE_UP" to ensure that small images are scaled up.
(3) Set imageScaleMode="FILL" to completely fill the image area with your main images. (Please note that cropping will occur if the aspect ratio of the image area does not match that of your main images.)
(4) Change the dimensions of your gallery (either increase the gallery width or decrease the gallery height) so that the image area itself is square which would allow portrait and landscape images to be displayed at the same size.
If you continue to experience difficulties, please post the URL to your gallery so that I can take a look and help further.
SimpleViewer Support Team.