Index: network.php
===================================================================
--- network.php	(revision 13656)
+++ network.php	(working copy)
@@ -286,17 +286,14 @@
 RewriteBase ' . $base . '
 
 # uploaded files
-RewriteRule ^(.*/)?files/$ index.php [L]
-RewriteCond %{REQUEST_URI} !.*wp-content/plugins.*
-RewriteRule ^(.*/)?files/(.*) wp-includes/ms-files.php?file=$2 [L]
+RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]
 
 # add a trailing slash to /wp-admin
-RewriteCond %{REQUEST_URI} ^.*/wp-admin$
-RewriteRule ^(.+)$ $1/ [R=301,L]
+RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]
 
 RewriteCond %{REQUEST_FILENAME} -f [OR]
 RewriteCond %{REQUEST_FILENAME} -d
-RewriteRule . - [L]
+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]';