I noticed a problem on one of my thematic sites this morning. I accidentally typed the wrong page URL but instead of Apache sending a 404 error, I got a page that seemed like a half completed single.php but with no content. The body class didn't contain "four04" and I think thematic got a little confused.
After much messing about I think I've found the cause. My permalink structure was set to:
If I change that structure to something like:
...the problem goes away and I get the proper thematic 404 page with search box.
As an experiment I installed Hybrid on the same server but a different domain (with identical config files). Hybrid doesn't get confused by:
...and correctly shows me its 404 page.
Anyone any idea what's going on?