Wordpress Bug: Text 'PHP Fatal Error' in Body

I was having trouble saving my last post (back when I was using WordPress), apparently because it contained the following content:

'PHP Fatal Error' in the post text triggers a bug

When you paste that into a new post and click preview, it actually shows a preview for the previous post! After returning to the posts list, I’m not even able to edit it again, it triggers a 404. But the content made it to the database OK: I was able to verify it with mysql on the command line.

Various substrings do not trigger the erroneous behavior.

I don’t know what the heck is going on. I tried greping around in the WordPress source code, but wasn’t able to find anything that looked like it was treating that text as a special case.