Hierarchy objects deleted and 999+ errors when adding terrain

-Here Is a picture of my problem. I closed my project and when i started it up again everything in the hierarchy was deleted. I had 10+ items there that just got deleted and when i tried to add a terrain i got over 999+ errors saying "instance: Terrain." and "Failed reading from 'SomeNumbers and letters' " and "Failed creating system: SomeNumbers and Letters" This has happened to 3 of my projects and i have tried to reinstall unity, but it still doesn't work.