I also have this problem. I have a valid htpasswd file and a valid htaccess which prevents /members/pdf/file.pdf
http://www.mysite.com/members/pdf/file.pdf correctly requires password and works.
However, I also want the same passwords to protect an article called members and other articles such as members/meetings etc
http://www.mysite.com/members and http://www.mysite.com/members/meetings display an error 500.
Any ideas anyone? A valid .htaccess would be ideal…