Run Optimize Catalog... from the File menu. Does it succeed?
Thank you for your reply.
I have done as you suggested and opened and closed couple of times but will have to give it a few days before I know if it has worked, will keep you posted
I'm afraid I am still having the same problem i.e LR could not back up the catalog.
This is happening too often, does anyone know how to fix this before I lose my catalog. Can I start a new catalog .
Where is the backup saved to?
Try a different location.
I backup to an external RAID drive same as my images, I have started a new catalog and I am going to transfer all of my files into it a few folders at a time and then close and save each time to see if it remains stable.
I have noticed that a lot of my backup catalog folders do not have an lrcat file only Previews.lrdata files and perhaps that is part of the problem.