I get a Page Not Found message for a post I've just published

I’ve just published a post on my website, http://clubphotointernational.com/. I can see it on the front page and I can see it in the posts on the dashboard. But if I click on the post from the front page, or try to View post from edit, I get a 404 message. What am I doing wrong? I’ve done this many times before and it’s always worked.

Thanks!