Multi-blog installation; all links redirect to home page.

I installed WordPress over the weekend, made it multi-blog, and successfully put several courses online. Then, about an hour ago, I was working on one of the course blogs when I noticed that all links suddenly started redirecting to my home page.

All the posts seem just fine in the database.

This page

http://jerz.setonhill.edu/stw/

should point to a course called “Seminar in Thinking and Writing,” but instead it points to my home page.

I’ve already assigned homework… sigh.

Here’s the contents of my .htaccess file — it’s too complex for me to figure out. I would welcome any help.

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]

# uploaded files
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ – [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]