FAQ Mac OS Classic
1. You get an exception at start like: 'java.lang.NoClassDefFoundError: javax/swing/UIManager'
The JFC/Swing libraries are not properly installed. You can download those libraries at http://java.sun.com/products/jfc/ (or directly http://java.sun.com/products/jfc/download.archive.html).
After downloading and unstuffing, copy the 'swingall.jar' file in your 'System Folder:Extensions:MRJ Libraries:MRJ Classes' folder.