I am using Firefox 3.6 on Linux and I have Java 6 update 15. Obviously I am using the newer plugin type.
Whenever I open a page with a Java applet it just becomes unresponsive and hangs. I tried with Chrome. I think it detects the Java plugin from Mozilla's plugins folder. Due to the multiprocess architecture it doesn't hang and shows the initial applet loading window but then it reports that the plugin has crashed.
The only way I can run Java applets is to download the class file and make an HTML file and run the applet using applet viewer.
Edit: I am here adding a crash report and this shows that there is problem with native system libraries: http://pastebin.com/mcL1MRHD.