Have been trying to repair this for a few weeks. See some similar problems and suggestions on internet, but nothing so far has worked or I didn't understand the suggested fix in order to enable it. Desperately need my thumbnails back! Only have thumbnails for text documents, which I believe use another program to generate them. This seemed to happen immediately after I repaired the grub as the disk was booting. Booting up fine now, but no thumbnails. Can't remember if I asked it to install the latest version of grub. Help gratefully appreciated! I have hundreds of thousands of photos I can't do much with without thumbnails!