Environment: Ultra 10, Sol 10, Mozilla
JRE Build: 60

1) Disable the cache in the ControlPanel
2) Go to the following URL and wait until the applet is fully loaded:

http://sqeweb/deployment1/deployment_tiger_master_ws/deployment/src/plugin/phonehome/applethtml/GrayBoxTest-07.html

3) Exit out of mozilla and then restart it
4) Go back to the URL mentioned above
5) Once the graybox animation begins, click on the browser reload button.
6) As soon as the animation begins again, click on the reload button again.
7) Repeat step 6 a few times and then applet will fail to load.

I can reproduce this most of the time. I've also attached the output from the console to this report.