Livery isn't working - even with unity and firefox

So, as I look like I may clinch the title today in Brazil for the first time in elite, I thought I could make a Brazil-style livery for the race (I have been on my current livery for a long time) but, even having reinstalled unitywebplayer several times, it won't work. I am using firefox, and I am still subscribed, yet when I load up the editor all that happens is a unity loading screen, then a black screen with 'loading' on it which I can never get past. I have searched a few forum posts so far and I still don't know the answer. Any help? (Ideally before 8 PM GMT today)

Have you tried restarting your computer as well?

Run Firefox in administrator mode and try that.

Yep, but nothing.On closer inspection, the black screen with 'loading' enscribed doesn't seem related to Unity at all, so I assume it is fake. Anyone else tried loading it and this came up?

That always comes up black screen with loading wrote on it then it comes up. Try rebooting you're router might be lag in your connection.

Has been rebooted, nothing :( I don't have anything else that lags, so hmmm.

I've left it loading for 20 minutes now....

If James' suggestion doesn't help, if you are running Windows, I would suggest doing a system restore back to a reasonable date.

Just went on a different computer and it works?!?!?

Go for a system restore then. LOL.
Something is getting in the way.

On the other computer run ADWCleaner. Remove all that it finds. Once it has finished restart the computer.
http://www.bleepingcomputer.com/download/adwcleaner/

You could always clean the system without doing a system restore. :)

Select the keyboard shortcut Win+X, and click Command Prompt (Admin) on the drop down menu. Type cd\ and press ENTER.
Type or copy and paste the command "DISM.exe /Online /Cleanup-image /Scanhealth " without the quotes and press the ENTER key.
Type or copy and paste the command " DISM.exe /Online /Cleanup-image /Restorehealth" without the quotes and press the ENTER key.
Make sure you include the spaces where indicated. These procedures can take a long time to complete so you need to be extremely patient.
Type exit when it completes, press the ENTER key and restart the computer.

If you get an Error 87 response recheck the command you entered. :)