Yes, everytime when I backup using the Backup when lightroom next exits. A I said in my original post I tried after creating a new catalog, with the same results.
And Johan I tried using the middle button and saving to my desktop and other directories all with the same failure.
Since I posted I found this https://helpx.adobe.com/lightroom/kb/unable-to-back-up-catalog.html
And by coping the config.lua file to my Presets root directory he problem resolves.
I just can't believe this know issue has been brought across to the new version !