[Plugin: Better WP Security] login issue – error message regarding pluggable.php

I installed and activated Better WP security, activated the basic security features, and then logged out. Now when I try to access /wp-admin, /login, or /admin, I get the following error message:

Warning: Cannot modify header information – headers already sent by (output started at /home/cec_admin/cecenter.org/wp-config.php:38) in /home/cec_admin/cecenter.org/wp-includes/pluggable.php on line 881

I have tried deleting the Better WP security plugin, and .htaccess, but the issue remains.

http://ww.wp.xz.cn/extend/plugins/better-wp-security/