Firefox Forum Issues

I've been having difficulty posting new threads for a couple of weeks with Firefox. Until now I could just refresh and it cleared up, now I can't post. This only appears to be the case with Firefox, Chrome seems unaffected.
On the main Competition page - or any page on the website, I can't see any of the sub-forums. When I select New Thread the page comes up, but there are two boxes for the text, one looks like forum code. The dropdown boxes for links and pictures don't work.
I've tried rebooting the browser and my PC, deleting all the cookies for the site, none of this works.
Anyone have any ideas of how to fix this, or where I should go to get a forum dev to have a look at it?

Thanks in advance.
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