Having trouble installing Java Plugin for Firefox on Mint 12

Hi all,
I need to use Revenue's ROS system and in order to do so I need to have the Java Plugin for Firefox working. It isn't so far.

I have checked about:plugins in the FF address bar and there's no mention of Java, so it's not there for sure and the testers say it's not working anyway. Flash player etc. all listed and working fine.

I am 99% sure my FF plugins are located under...

/usr/lib/mozilla/plugins

...as they all correspond to what's being reported under about:plugins and this seems to be (from googling) where FF loads its plugins from.

I use a JDK as I use this machine for Java Development under Eclipse so Java (6) itself is certainly installed and working.

I closed FF and created a symlink...

libnpjp2.so

...in...

/usr/lib/mozilla/plugins

...to point to my Sun Java 6 plugin here...

/usr/lib/jvm/java-6-sun-1.6.0.26/jre/lib/amd64/libnpjp2.so

(note the location is slightly different to the user instructions given by Sun here because a) my machine is 64 Bit and b) it's a JDK install of Java, not a JRE as I need the JDK for work.)

I restarted FF and it isn't working. What on earth could I be missing here?