Nagios Config Error

Starting nagios:CONFIG ERROR! Start aborted. Check your Nagios configuration.

I am trying to monitor router/switch but every time I open the nagios.cfg file and remove the # of this line cfg_file=/usr/local/nagios/etc/switch.cfg to start monitoring router/switch I receive the above error message. If I reinstalled the packages and plugins will be able to monitor the host where nagios resides but will not allow me to touch the nagios.cfg to monitor router/switch. Once I open the that file I receive the above error message. Any idea what’s causing this to happen?

do a /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg in console to see the exact line what’s causing this message

Thanks for your prompt reply. I tried that same issue. I will go ahead reinstall fedora and nagios and see what happen.