unable to logout

i added a link for user to log out, but it seems that sometimes doesn’t work.

http://domain.com/?password-protected=logout

the following link will be loaded, login is not required.
http://domain.com/?password-protected=login&redirect_to=http%3A%2F%2Fdomain…

is it something wrong with my setting?

thanks

http://wordpress.org/extend/plugins/password-protected/