Htaccess password & piwik problem

Hi all,
the problem is that the htaccess popup password appears on every page instead just in the piwik directory.

these are my settings:

Main wp htaccess (default):

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

piwik folder htaccess:

AuthType Basic
AuthName "unauthorized access"
AuthUserFile "path-to-my-passwd.file"
require valid-user

Infact disabling the plugin that call piwik tracking code (“piwik analytics” plugin) the problem doesn’t occurs. Furthermore, disabling the above plugin and placing manually the piwik tracking code in the footer body, the problem occurs once again.

Have you any suggestion?

Thank you,