The posts in WordPress have been deleted automatically. They are no longer in the trash and when I checked the database, they're all gone. When I restored from a backup, I recovered all of the posts again. I repaired the tables. They're all gone again--completely wiped from the database.
Could there be something in the WordPress core that is causing this problem? I contacted my web host, Media Temple, and they said this sounds like an issue with WordPress.
Any advice will be helpful.