[Plugin: WP Multi Network] Permalink not working

I got some problem to make the Permalink working. Let say I got 2 sites. site1.com and site2.com(I setup site1.com first and then add site2.com through WP Multi Network plugin

Network Name: site2
Domain:: http://www.site2.com
Path: /
Site Name: site2

I can go to the site2.com home page and the admin page. But if I click on the hello post (e.g. http://www.site2.com/2010/11/18/hello-world/), it just redirect me to the site1 home page (i.e. http://www.site1.com).
Does anyone know what’s going wrong? Thanks a lot.

My code in wp-config.php

define('WP_ALLOW_MULTISITE', true);
define( 'MULTISITE', true );
define( 'SUBDOMAIN_INSTALL', false );
$base = '/';
define( 'DOMAIN_CURRENT_SITE', 'www.site1.com' );
define( 'PATH_CURRENT_SITE', '/' );
define( 'SITE_ID_CURRENT_SITE', 1 );
define( 'BLOG_ID_CURRENT_SITE', 1 );

My .htaccess

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]

http://ww.wp.xz.cn/extend/plugins/wp-multi-network/