Posts are not shown in Admin or main site

All of a sudden today posts started disappearing.

1. First, when logged in as an administrator, dashboard showed 0 posts, and no posts could be shown on site.
2. When logged out as an administrator, posts showed on main page of site, but when permalink was clicked, “Nothing found” returned.
3. However, at the bottom of “Nothing found” page, was a list of all posts (although clicking on them returned “Nothing found.”
4. Now, however, nothing is shown whether or not I am logged in.
5. Comments still show in admin, even still linked to post title.

I have tried switching themes.
I have disabled all plugins.

Nothing works.

Help!