I don't know if this will help but it helped me. In most of cases i saw that people uses different Sizes and formats for there Pictures in the gallery.
- 1. Be sure u use unique format ie: only JPG or only PNG, ect.
- 2. Be sure you use only unique size ( ie: all thumbnails / pics are 150x150)
- 3. If you look at the settings in the Gallery (see attachment), be sure you DO NOT leave the WIDTH & HEIGHT on AUTO (if possible)-
That is not only better for every Loadingtime and Browser it should also solve your displaying issue in IE 8 and 9.
I hope that helps a few people.