As of this writing, Mac OSX users who have jmsl.jar in ~/Library/Java/Extensions will get an AccessControlException when some threads are interrupted in an applet context.

One workaround is to create a file named .java.policy in your user home directory (note that the name must be "dot java dot policy")

The contents of .java.policy should be as follows:

grant codeBase "file:${user.home}/-" {
	permission java.lang.RuntimePermission "modifyThread";
};

Quit your web browser and reload the applet and it should work.

Currently, this behavior is filed as a bug with Apple Developer Connection Bug Reporter, 
Title: "Thread.interrupt() exception when jar in ~/Library/Java/Extensions", 
Problem ID: 3677803


Nick Didkovsky, June 3, 2004

Thanks to Kimo Johnson for this .java.policy workaround.