I have had this problem myself and the great guys at Xamo helped me figure it out...
instead of using the htaccess to list the sites that you are allowing to view the material..
I just had a folder in a website that wasn't taking members hold all my content... if your doing this too.. just make an htpasswd file and create a user and pass.. then read the following :: If this is not what you mean or you need more help let me know ....
When you link to the shared area, just use a link such as:
password@sharedcontentarea.com>
http://username
assword@sharedcontentarea.com
That should allow you to protect it and only allow authenticated users access to this area.