This is usually because the folders.dbx file is missing or damaged. With OE closed, use find-file to find folders.dbx and rename it to folders.old and re-start OE. You should get a new folders.dbx file.
Samsung Galaxy S8 review
1995-2015: How technology has changed the world in 20 years
This 2D animation about monsters is illustrated in a Van Gogh painterly style
How to get WWDC 2017 tickets
Synology invites you to visit them at Insomnia on 26th – 29th August. Book your tickets now and visit Synology.