I installed this comment all plugin and got this error:
Fatal error: Call to undefined function pnfa_get_users() in /home/tdg/public_html/wp-content/plugins/wp-comment-notifier-for-all/wp-comment-notifier-for-all.php on line 282
so looking thru the code - line 282 - i saw that there only was many cnfa and one pnfa referenced. I changed the 'p'to a 'c' and the error went away. maybe typo??
hope it helps =)