Subpages return 404 error

I set permanent link as http://site.com/%postname%/.
I’m talking about this type of pages: http://codex.wordpress.org/Pages_Screen.
All first level pages work fine. But subpages don’t.

For the first level page I get url like this: http://site.com/page/.
For the second level page – http://site.com/page/subpage/.

If I use permanent link http://site.com/?p=123 or http://site.com/2012/02/29/sample-post/, subpage works fine then.

How does make it work with http://site.com/%postname%/ mask?

Added:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

Update:

I found the reason. It is a post_type field in the wp_posts. But I cannot find out where this field is saved?

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