I had the same problem with sun-java6-jre today until I manually added symlink to /etc/alternatives/firefox-javaplugin.so in /usr/lib/xulrunner-addons/plugins.
I had the same problem with sun-java6-jre today until I manually added symlink to /etc/alternativ es/firefox- javaplugin. so in /usr/lib/ xulrunner- addons/ plugins.