I decided to clean up the history of Firefox
All ticks were applied except for
Cookies which are not protected and saved passwords.
All appeared to work but on restarting FF I found some sites were not loading correctly and displaying wrongly. I checked with IE and the sites were correct. To resolve the problem I ran FF option/privacy/private data all checked except saved passwords - clear now and all was back working.
I do not know if this was a one off but it seems AU did not clear all files correctly.