Multisite install (subfolders) not showing new sites

I just see white pages, as in https://cassandradisque.com/oncefabulous/2010/12/13/hello-world/ and https://cassandradisque.com/oncefabulous/2010/.

This is a new install. I’m not showing any errors anywhere. I was able to set up my sites just fine in the admin panel (though I can’t see any of them). I have all my plug-ins deactivated.

I’m thinking it’s likely an .htaccess problem, but I don’t know where to start, so here’s what my file looks like:

AddHandler application/x-httpd-php5 .php
# BEGIN WordPress
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).*) $1 [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(.*\.php)$ $1 [L]
RewriteRule . index.php [L]
# END WordPress

Thoughts?