virtualhost maximum limit (?)

i've an httpd.conf with 520 include "conf/nnnnnnn.conf"
if i add some new, i get a blank page , this includes are in the form:


<VirtualHost 216.162.42.11:515>
ServerName dantefreakjournal.zger.com
DirectoryIndex index.php

SetEnv USER_ID 640
SetEnv ZBLOG_ID 595

DocumentRoot /var/local/sdapache/htdocs2//home/640/

RewriteEngine On
RewriteRule ^/$ "http://dantefreakjournal.zger.com/pagine/index/....html" [R=permanent]

Alias /pagine/ /var/local/sdapache/htdocs2//pagine/640/595/
Alias /dinamico/ /var/local/sdapache/htdocs/
Alias /admin/ /var/local/sdapache/htdocs/admin/

ErrorDocument 404 /dinamico/cache.php

<Directory /var/local/sdapache/htdocs/>
SetEnv USER_ID 640
SetEnv ZBLOG_ID 595
Options -Indexes +Includes +FollowSymLinks
</Directory>

ErrorLog /var/local/sdapache/logs/640_595_error.log
CustomLog /var/local/sdapache/logs/640_595.log combined
</VirtualHost>

in front there is an apache that proxy requests on post 515

what is the problem?
thanks.
Valy