If you are a user of the GNU Image Manipulation Program (GIMP) on OS X, and you’ve upgraded to Leopard, you’re likely to run into some snags. You should instead go here to update your X11 installation, and then here to get the appropriate version of GIMP. Note that this is the new 2.4 version, with a lot of improvements from 2.2. They also have a more “edgy” and modern-looking icon for the app.