Are you sure you have the latest Java? I am going by what the site said, and by what i know about Java and Javascript. They are not the same. Javascript is what is used for things like Greasemonkey Scripts and the likes. Which are used to block or modify sites and how they work.
Opera has a whole list of User Javascripts that they have going along with Firefox having them as well.
NoScript blocks these JS from running. As do AdBlock and AdBlock Element Hinding. Along with the afore mentioned Greasemonkey.
So you will have to check and make sure that you dont have any GS, NoScript or anything else running. Because those are the main differences between someone running IE and someone running Firefox is the extensions they use in firefox. So it has to be a extension you are using.
I can get it to work in Firefox by jsut allowing it through noScript. I got it working in Opera by not running my User Javascript files. So it does work, it is that you have to find out what extension you are running that is causing it from not working.
the setup can be exactly the same. That doesnt matter. What matters is the extensions.