Hi, I had problem launching iXAFS on Mountain Lion after the OS upgrade. It seems the path to X11 might be hard wired in the program. Here is my workaround solution by creating a symbolic link to XQuartz. It might be worth sharing the trick. 1. Install XQuartz 2.7.4 from http://xquartz.macosforge.org/landing/ 2. Launch Terminal.app and issue the following commands: 2.1) cd /Applications/Utilities 2.2) sudo mkdir X11.app 2.3) cd X11.app 2.4) sudo ln -s ../XQuartz.app/Contents 3. Now either double-click on iXAFS.app or command line `open -a ixafs` should work -- Tsu-Chien WENG Stanford Synchrotron Radiation Lightsource 2575 Sand Hill Road, Mail Stop 69 Menlo Park, CA 94025, USA +1-650-926-4107 (office) +1-650-926-4100 (fax)