Ok, after playing around, I got it. Changed my .htaccess to:
Options +FollowSymLinks
AddDefaultCharset UTF-8
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^plugins.xhtml articles/plugins.xhtml [R=permanent,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-l
# Administration URL rewriting.
RewriteRule ^admin(.*)$ admin/index.php?$1 [L,QSA]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-l
# Main URL rewriting.
RewriteRule ^(.*)$ index.php?$1 [L,QSA]
</IfModule>
Adding that first RewriteRule in. While you're reading this, could someone tell me what the !-l, !-f, and !-d mean?