Thank you for your help in this matter. I have at least solved the problem in part. I had a problem with my browser and triggered an earlier restore point. I have now put my computer back to where it was before this . Lightroom is now back, but unfortunately I have still lost the book I was working on and the flags picking out the required images. I am assuming it is now back to 4.3 and the bug existed in 4.1 before I downloaded the upgrade.
I am sorry that I did not reply to you earlier but I am new to forums and I couldn't see where there was a reply button.