On my computer it wasn't so much Java as the chat application that was being blocked. You have to go into the Java secutiry settings and directly enter the chat url but the client url in order to allow it to bypass the security. I shall see if I can take a few screen shots of what I had to do. Although I do use a mac so this might be slightly different.
If any one can say how to clearly access the Java Control Panel on Windows this could be very helpful.
So the first step on a mac is to open your system preferences, this should look like this:
Once it has been opened, you will need to click on Java down at the bottom. This will open the Java Control Panel, and should look like this:
This is where I am assuming it will become the same for both Windows and Mac users once at this stage (As you can see I am running chat in the background so this clearly worked for me).
From this point you will need to click on the Security tab at the top of the Java Control Panel. Once click it should appear like this:
Now as you can see in order to run chat you do not need to reduce your secutiry level. I would leave this at high (unless changed for another reason). What you do need to do is add two URLs to the exception site list. (I needed both in order to run the chat room so I would recommend that both are added in order to make sure it is working).
Here is a close up of the URLs that need to be added:
You must click on Edit Site List and then click on Add in order to 'Add' both of these URLs. I can add another screen shot of this stage if somebody needs it seems quite self explanatory.
You may also get a security warning when you try to open chat but just click run and hopefully (fingers crossed) it should run fine.
Again I apologise if this does not work for Windows users having difficulties but it should hopefully work for Mac users with the lastest software.
Please let me know if this does work for Windows or if there is any extra help you might need.
Feel free to PM me for further help if needed. Hope this helps,
Karl.