Fixed. This is your WP .htaccess file now:
Rich (BB code):
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /store
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^.*$ index.php [L]
</IfModule>
# END WordPress
I removed the ending / from the RewriteBase, and I changed the last RewriteRule which had two problems.
1) The URI match was just
. which would only match one character, so I changed it to
^.*$ which will match any URI, just like XenForo's .htaccess file.
2) I removed the beginning
/ from the target location so it's just
index.php instead of
/index.php. One is relative, the other is not.