Pages not loading within Password Protected Directory - .htaccess

Question

I have password protected a directory called 'admin' using the usual .htaccess method:
AuthType Basic
AuthName "restricted area"
AuthUserFile xx.xxx.xxx.xx/public_html/admin/.htpasswd
require valid-user
When I load the home page of the site which is password protected, I log in and home page loads fine, but then when I click a link to load a sub-page, the home page just reloads. There are links which open pop-ups and these pop-ups are also containing the home page when they should be loading forms etc..
Is there something missing in my .htaccess file?

Answer 1

I have a Wordpress install in the root with its usual htaccess but this admin directory is created from a subdomain so is (or should not be) affected by the Wordpress htaccess.
If this subdomain is pointing to a subdirectory off the main domain's document root (which is what it looks like) then the parent directory's "WordPress" .htaccess will affect this. .htaccess files are inherited along the filesystem path.
Since WordPress uses mod_rewrite you can prevent mod_rewrite from being inherited by simply enabling the rewrite engine in the subdomains .htaccess file:
RewriteEngine On
AuthType Basic
# etc...
Other modules will still be inherited, although the default WordPress install does not use any other modules.
Alternatively you can try adding an exception to the parent directory's .htaccess file, in order to exclude it being processed when accessing the subdomain (or rather only process it when accessing via the main-domain). Add the following to the top of the WordPress .htaccess file:
RewriteEngine On
RewriteCond %{HTTP_HOST} !=example.com
RewriteRule ^ - [L]
Where example.com is your main-domain. Which basically says if the host is not the main-domain then abort.