I discovered a bug in Apples implementation of Java. When selecting multiple leaves in a JTree, and then ctrl + drag, the mouseDragged event should be fired. However, on a Mac, the mouseDragged event never fires!
We tested on Linux and Windows, and everything works. Argh. At any rate, hopefully Problem ID 4814103 will soon be fixed:-)
Not sure if others can see it, but the site is here https://bugreport.apple.com.
The joys of doing Swing development!