Thanks Chris, apologies for the delayed response.
I have tried using both Firefox & Google Chrome browsers with no joy. I have removed all notes (although there were only 14 characters used) and I have played with the names and address in order to shorten these fields as much as possible (although none of these fields are excessive) however I am still having no joy in updating the clients address.
The error message doesn't appear to direct me to any particular field and there are no fields highlighted to show an error in any way.
The Serial number is ***8056
We are still at a loss so any help would be much appreciated.
Thanks, Kat