.htaccess problem 2 wordpress on 1 hosting (no multisite)

Hy,

I need help for setting up my .htaccess file to the following situation: I have 2 wordpress website on the same principal hosting (ivalentin.ro) and a website (addon domain) let’s say second.ro for example, in second.ro subfolder. My current file on root .htaccess it is slightly modified from the basic WordPress configuration for security and now looks like this:

AddHandler php5-fastcgi .php
Action php5-fastcgi /cgi-bin/php5.fcgi
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteRule ^admin=ivalentin$ %{REQUEST_URI}/ [R=301,L]
RewriteRule ^admin=ivalentin/(.*?)$ /wp-admin/$1?%{QUERY_STRING} [QSA,L]
RewriteRule ^autentificare/?$ /wp-login.php [QSA,L]
RewriteRule ^forgot/?$ /wp-login.php?action=lostpassword [QSA,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

In these conditions when i access second.ro i receive 500 – Internal Server Error. If i remove the .htaccess file in the root, everything is ok. Now i can only acces it form ivalentin.ro/second.ro How do I change the current htccess file to directly access second.ro site?

Thank you in advance !