Comment on WP Autoblog Plugin Support by SEO Dave.
I would hazard a guess you are using Frontpage as an HTML editor, because it’s a WYSIWYG (What You See Is What You Get) type editor it doesn’t always maintain HTML/PHP code as it’s meant to be. Also I understand uploading a file with FrontPage can mess up the code within.
If you are using FrontPage to upload etc… try using an FTP program like Filezilla instead.
If you aren’t familiar with FTP, you might be able to upload the file using Frontpage and edit it via the built in WordPress theme editor and copy and paste the entire contents of the file over the presumably messed up code.
If it’s not that there’s a forum thread at it’s a server/setup issue related to no default document. Normally a server will include a default document list like index.html, index.php. It seems if your server lacks this part of the setup, if a file isn’t present you get this sort of error instead of a 404 error page.
If it is this would also suggest the multisite template page is broken/absent as well to generate a 404 error (missing page).
I don’t think it’s a big deal if this isn’t setup on a server, just means you get weird errors when a page isn’t present. You might be able to test this by trying to load a page on your site that doesn’t exist, you should receive a 404 error page.