Password Protected Page URL's format

Hello!
I’m using WordPress 3.5.1

I want to protect a page and it works fine with my full URL:
https://www.airstar-asia.com/test

But I’m redirected to /wp-admin when I don’t type “wwww.”:
https://airstar-asia.com/test

Password is “password”

Additional infos:
Permalinks: https://www.airstar-asia.com/%postname%/
htaccess content:
# 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

Tests:
– All Plugins have been desabled
– I’ve tried to switch to the basic theme but I still have the same issue.

Is it possible to fix this issue?