404 Error with Pretty Permalinks, 3.1.1 and Yahoo

Problem Site: http://thereasonfortears.com/blog/
Host: Yahoo
Description: 404 error with the /index.php/%postname%/ Permalink structure.

This problem began immediately after I made my latest post, about 2 hours ago. I haven’t updated any plugins recently. The posts look fine on the index page, which calls up the latest posts. While I was writing the post with the permalink the preview also showed up fine.

But once published, previewing, viewing “more” of the post or going to the post directly do not work. I am running my site using TWO separate WP installations. One for the main site and one for the blog. It is only the blog subdirectory that is not functioning (though only the blog subdirectory uses Posts). There are no other differences in plugins/updates between the two.

Notes:
1. I’ve already disabled ALL plugins (reenabling one: Cricket Moods so that the posts can actually be seen)
2. I have uninstalled wp-cache so that is not a cache problem. I have no wp-content/cache/ folder.
3. Links DO work with the default permalink structure but all my linkbacks are with the ‘prettyish’ permalink structure above.
4. I updated to 3.1.1 when it was released, it has been a while.

Because i’m Yahoo I do not have access to the hta file.

Please do not tell me to change hosts. I’ve already paid up the year and It’s not an option.