Thanks Shegnada. He had already tried to delete the project from within PT and then S/R again, but to no avail. Yesterday I sent him a backup file and he has restored this ok. I asked him to try S/R again, to see what happens, but I think he is afraid to lose the books again, and so hasn’t tried!
From your reply, it thus sounds like the problem isn’t on his machine - so where / what would the problem likely be?