Fortunately Ubuntu allows for users to change the Java version used and also run multiple versions of Java. To do this:
1. Download JRE 6u11 from here:
2. Chmod +x it. i.e.:
sudo chmod +x jre-6u11-linux-i586.bin
3. Move it to the jvm folder
sudo mv jre-6u11-linux-i586.bin /usr/lib/jvm/
4. cd to that folder and run it
5. Now add it to the alternatives:
sudo update-alternatives --install /usr/bin/java /usr/lib/jvm/jre1.6.0_11/bin/java 500
6. Then you can select to use that version of java by running:
sudo update-alternatives --config java
Now that's all well and good; but it will still be running the newer version in Firefox. So:
7. Run the java control panel, by typing:
Then click on the tab 'Java' and the button 'view' under 'Java Applet Runtime Settings'
From there, you can disable any unwanted Java versions.
8. The plugin inside Firefox's setTest your Firefox java version here:
Unfortunately my Cisco PIX 501 Manager STILL does not work with this.