I was not able to view the applet you have posted (the first message). May be that is the reason why the Safari did not response.

There might be other reason to cause browser unresponsive. e.g.
If I viewed java applet with Firefox 2 with JDK 1.6.0_06 , the browser will hangup (when java embed in the html).
You can find out similar report at http://forum.java.sun.com/thread.jspa?messageID=10221200

Now,  I switch to Foreox 3 and install latest JDK1.6.0_07 and it work just fine when I view other topic.
May be you can try to update to latest java run time.