Thanks chaps,
Following your replies I found some other threads related to this - it seems quite a common problem. Anyway I found this thread where Dariusz has provided the Reg add commands. I entered these and confirmed that I have integrated auth enabled within IE advanced settings. I can now log on to Web UI using IE. However I still have the same error message in Chrome & Firefox. It is not the end of the world as we can use IE but I just wondered why this might be?
Many thanks for your continued help. Happy to say we are now mostly up and running with AMT.
Regards,
Graham