Took me a while to figure out the problem.
My top right widget slideshow at http://www.stokrozen.nl is displaying all images from all [nggallery] (thumbnails) galleries and each image is displayed full shape reduced size within the defined bounds. Perfect.
But one gallery is set up as [imagebrowser] and this single portrait photo is stretching and not behaving.
There are only a few images to see so just click on the slideshow to roll through and see the problem.
Pretty sure it is a conflict between the slideshow and [imagebrowser] request. Anyone else know about this?