All posts disappeared.

After I wrote a new post and published it, all the posts I ever wrote have vanished from my blog.

I get the standard “Sorry, no posts matched your criteria.” message.

I get the same message when I click on one of the categories.

My pages are still visible.

I know the posts still exist in the database, because when I click a link on one of pages, that links directly to a single post, it works fine.

In the admin section, when I click Manage, not a single post shows up.
However, on the Dashboard I see the posts in the Latest Activity, and I can edit every post when I click on them there.

When I closed and reopened my browser, suddenly an error message was visible:

SELECT DISTINCT * FROM wp_posts LEFT JOIN wp_post2cat ON (wp_posts.ID = wp_post2cat.post_id) LEFT JOIN wp_post2cat AS sem_post2cat ON sem_post2cat.post_id = ID WHERE 1=1 AND post_date_gmt <= '2006-05-28 13:33:59' AND (post_status = "publish" OR post_author = 1 AND post_status != 'draft' AND post_status != 'static') AND post_status != "attachment" AND sem_post2cat.category_id = 3 AND post_date >= '' GROUP BY wp_posts.ID ORDER BY not (ID in (58)), post_date DESC

Maybe you can see for your self here, but it doesn't always show up

I've narrowed the problem down to this:
When I overview the posts in the Latest Activity, my last post is there, and so is the post I wrote yesterday. But not the one I wrote earlier today.

When I view the latest post, I usually see a link at the top, pointing to the previous post. That link now points to the post of yesterday, skipping the real previous post.
(click)

However, I can now access the missing post, when I edit the post ID in the address bar (click) and it looks fine!

So, I think the problem lies in post with the ID 122, but what is it?
How can I fix it?