Nagios Support Forum

I was able to fix this issue by changing the owner of the config files to "apache". Once in a while these files will get set to nagios.nagios so you have to go back in and reset the permissions. Hope this helps :D Command: chown apache.nagios /usr/local/nagios/etc/*.cfg *note* You may need...

I am having the same issue as well.

Although you can still add/remove/edit through the core config manager, adding anything using the wizards will cause the hosts added to become "stuck" and no longer editable from the web interface.