Then I don't understand the question. You should not have had to 
 touch the configs and the suid part would be provided by a binary 
 wrapper in usr/share/BackupPC/sbin/BackupPC_Admin. 

I followed the instructions in this blog:  
http://ftanada.wordpress.com/2012/10/18/install-backuppc-on-centos-6-3/

Specifically 

"15. This time, edit the Apache configuration file.
nano /etc/httpd/conf/httpd.conf

Changes should reflect these changes:
User backuppc
Group apache
ServerName actual_server_hostname_or_IP_Address:80"


This is the step that breaks the Nagios web interface

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