We all take photos in both landscape and portrait modes. Photogallery has the tools to rotate the images, but there is a catch. If you select multiple images to rotate, it works OK. If the number of photos exceeds a screenful, you need to deselect the images just rotated before proceeding to the next  screen and selecting more piccies to rotate. if you don't do this, previously rotated images will be rotated again.

There ought to be an option to automatically deselect each image after rotation.