We have a multisite installed in the root directory (multisite.com) and also a wordpress single installation on a subdomain (help.multisite.com)

In the root .htaccess we placed:

#START Security: Disallow access to folders
Options All -Indexes
# END Security

On the main site (as expected we get)

"403 Permission Denied. You do not have permission for this request /wp-content/blogs.dir/83/"

Nice. :)

BUT. We just noticed that when trying to access the subdomains folders we get:

Internal Server Error. The server encountered an internal error or misconfiguration and was unable to complete your request.... Additionally, a 500 Internal Server Error error...

This is something we do NOT want.

So the question is:

How can we avoid the above result and make the message for the subdomains be "403 Permission Denied" (the same as for the main site and NOT "500 Internal Server Error" (as it is now)? We put what, where?