Hi folks.
All your files are safe

Backups are taken automatically every 24 hours.
I check that everything is running fine every so often and I always check to make sure that any new user is not there to load spam.
The last time I checked was two days ago and everything was fine. It seems that one of the program files became corrupted,. Perhaps due to some system maintenance.
I made a backup of the database and then reloaded the version of the system that was, or at least should have been, running and that seemed to solve the problem.
While I was logged in I then took the opportunity to update the software to the latest version just in case the issue was one which occurred because of a bug in the outdated version.
All seems to be running fine now. I will check again in a few hours and a couple of times during the day tomorrow.