Seen while running the latest nightly and latest Aurora. This works using the latest Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:12.0) Gecko/20100101 Firefox/12.0. This machine has been updated to the latest Java version via the Apple software update: java version "1.6.0_31". I have also seen this in the lab on 10.7.4 and 10.5.8 nightly builds. about:plugins shows File: JavaPlugin2_NPAPI.plugin Version: 13.7.0 STR: 1. Load http://mainline.brynmawr.edu/Courses/cs110/spring2002/Applets/Smiley/Smiley.html 2. Receive error message in attached screenshot. 3. Browser hangs and you have to force quit. The details tab gives the following additional information: load: class Smiley.class not found. java.lang.ClassNotFoundException: Smiley.class at sun.plugin2.applet.Applet2ClassLoader.findClass(Applet2ClassLoader.java:252) at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Plugin2ClassLoader.java:249) at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Plugin2ClassLoader.java:179) at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Plugin2ClassLoader.java:160) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Plugin2ClassLoader.java:690) at sun.plugin2.applet.Plugin2Manager.createApplet(Plugin2Manager.java:3045) at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Plugin2Manager.java:1497) at java.lang.Thread.run(Thread.java:680) Exception: java.lang.ClassNotFoundException: Smiley.class load: class Smiley.class not found. java.lang.ClassNotFoundException: Smiley.class at sun.plugin2.applet.Applet2ClassLoader.findClass(Applet2ClassLoader.java:252) at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Plugin2ClassLoader.java:249) at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Plugin2ClassLoader.java:179) at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Plugin2ClassLoader.java:160) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Plugin2ClassLoader.java:690) at sun.plugin2.applet.Plugin2Manager.createApplet(Plugin2Manager.java:3045) at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Plugin2Manager.java:1497) at java.lang.Thread.run(Thread.java:680) Exception: java.lang.ClassNotFoundException: Smiley.class

Needs a regression range for sure, but I did quickly go back to 20120409 trunk and it was broken in that build as well.

This doesn't happen with all Java applets, as far as I know. For example http://java.sun.com/applets/jdk/1.4/demo/applets/Clock/example1.html. Marcia, please test with that and let us know your results.

Another site that doesn't work for me: http://csis.pace.edu/~bergin/Java/applets.htm The site that Steven references works for me on my 10.6 machine using the latest nightly Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:14.0) Gecko/20120412 Firefox/14.0a1.

Here's the regression range I found on OS X 10.7.3, testing with both of Marcia's examples: firefox-2012-02-29-03-11-08-mozilla-central firefox-2012-03-01-03-11-35-mozilla-central This range includes the patch for bug 406541, which has already been implicated in a couple of other similar-sounding Java bugs.

Marking dup of bug 736965 These have the same root cause