irregular sized thumbnails

Hi The maxgalleria gallery seems to work in all aspects except some of the thumbnails display as much larger than the others. I have the thumbs as square, as there are 9 images, 2 of them are portrait the rest are landscap..but what it does is display the portrait ones as much larger instead of all as square. Not sure why this is..here is a link, whether i set as portrait landscape, square, the thumbnails display like this:
http://www.kimsoogoodtrack.com/wordpress/?maxgallery=the-home-series
thanks, been though sooo many gallery plug ins, this one actually works the best, Im using a theme called Tempera