RewriteRule for ‘virtual host’ pointing to subdirectory

i worked this out ….

i put this in my .htaccess

RewriteCond %{HTTP_HOST}        ^www.seconddomain.com
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*) /index.php/my-special-category/$1 [L]

#The default wordpress things
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

http://www.seconddomain.com/lorem-ipsum is showing
http://www.firstdomain.com/my-special-category/lorep-ipsum
correctly

but
http://www.seconddomain.com/
redirects to my http://www.firstdomain.com and i think it is something in the wordpress rewrite class that does something special for ^/$

anyone has a clue ?