I installed this on 4.1.8 and it works well once the images were moved to the file system.
For clickable thumbnails, I changed the content of thickbox/thickbox_productpage.tpl as outlined earlier in this thread. It works, but I then lose the numbers of the image, close or escape and the <prev next> ability. It also opens to a full screen. Had anybody worked out a better solution for clickable thumbs?