The normal.dot template has become corrupted. You should search for this file and delete all instances of it. When you launch Word again, a new normal.dot file will be generated, and your problem should be solved.
Hands-on: Samsung Galaxy S8 review
1995-2015: How technology has changed the world in 20 years
Samsung's beautifully designed Galaxy S8 makes for better VR experiences too
47 iPhone camera tips to help you take better photos
Synology invites you to visit them at Insomnia on 26th – 29th August. Book your tickets now and visit Synology.