Sadly the website was developed for IE only and there are checks for other browsers at the log in stage so a Firefox check is out the window.

I'm beginning to think it might be firewall or security software dependent but unfortunately given we don't host the live site ourselves, I'll have to contact the hosts and ask them their opinion.

I'll update this thread on my progress if I get anywhere.

If it helps, I can post up more code but I feel it will not help as I've checked it against the test server files and they match exactly.