I added those 2 lines of code in my .htaccess file and it solved the problem, thank you for your assistance.

I installed and used this plugin on my development server and everything was fine. After installing BulletProof Security plugin I started to get this error messages when ever I am trying to add a new gallery:

You don't have permission to access /wp-content/plugins/wp-simpleviewer/sv-config.php on this server.
Additionally, a 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request.

I checked the file permission and all folders have 755 and all files have 644. I set the wp-content/uploads folder permissions to 777 (full) but still no luck. I deactivated and deleted the plugin then reinstalled it but the problem is still there. I deactivated BulletProof then deleted Simple Viewer and reinstalled it but still no luck. Can anyone tell me what to do to make it work again? For sure it's a files permission problem but I really don\y know what could cause the problem.

Thank you!