Problem loading java applet with Firefox, but loads using Opera

[Nigel Henry]

I'm having problems with Firefox on some Java sites, not being able to 
load/initialise java applets. That is with the Java version available from 
the repo. This isn't only on Kubuntu Intrepid, but also on Debian, and 
Fedora, which have their own java packages. If I download, and install Sun's 
JRE, there is no problem with these sites. Example site below.

http://www.jigzone.com

The java test applet runs ok on Firefox, but not the jigsaw applet. Link to 
java test applet below.

http://www.java.com/en/download/help/testvm.xml

The jigsaw applet will load ok with Opera, but I do have to set a specific 
java path in Opera.

Opera's plugins list the GCJ Web Browser Plugin 0.96.1, but the default java 
path in Opera is insufficient. The path I have to set is below, and is 
accessable by going to Tools > Preferences > Advanced > Content > Java 
Options, and replacing the existing line with the one below.

/usr/lib/jvm/java-6-openjdk/jre/lib/i386

You need to restart Opera, after changing the Java path, then try the site 
above again.

Would anyone who has java installed (not Sun's Java), and Opera, like to try 
out what I've set out above, just to verify my experience.

I expect Firefox to not load/initialise the applet from www.jigzone.com, but 
Opera with the correct Java path to load, and display the jigsaw applet.

I suspect that /etc/alternatives has something to do with why Firefox cannot 
load the applet, and I can't find a way to specify a path to java in 
Firefox's about:config, whereas in Opera I can specify a direct path to java, 
bypassing /etc/alternatives.

This is all a bit academic, as the easiest route is to just install Sun's JRE, 
which works fine.

Any suggestions as to how to get the jigsaw applet displaying on Firefox, with 
the Java version available from the Ubuntu repo, will be very gratefully 
received.

Just passing the time, and trying to resolve a long running problem.

Nigel.