Nagios/Apache/Linus issue

Config:
Linux CentOS 4.6 2.6.9-78.0.1.EL
Apache/2.0.52 (CentOS) web-server
Nagios v3.0.2
mysql Ver 14.7 Distrib 4.1.22, for redhat-linux-gnu (i686) using readline 4.3
PHP 4.3.9

Installed Nagios v3.0.2 following the Quick Install Guide for Fedora by the book.
Nagios is working fine (mixed Windows, LInux LAN, misc IP devices, etc etc).
I’m a newbie to Nagios but pretty experienced with Linux, Apache, etc.

My problem is that Apache pages are now serving VERY slow compared to before the Nagios installation. For some reason these pages can now take up to 2 mins to fully load.
I thought initially perhaps a file permissions problem as the page with the Nagios link about half-way down half-loaded quickly and then stalled for up to 2 mins before the rest of the page loaded. But I host 4 or 5 virtual web-hosts on the same physical server and they are all now loading at a similar speed.
I have checked general network configuration pages (/etc/hosts, /etc/resolve.conf, /etc/sysconfig/network-scripts/ifcfg-eth0) and all appear as expected.

I did nothing in the configuration set up other than as described in the Quick Install page.
Any ideas anyone? Does the installation process manipulate general configuration details on a Linux box? If so what exactly?

TIA,
P

Turned out not to be a Nagios/Apache config issue after all.
In fact it turned out to be an ethernet-over-power issue that just happened to manifest itself around the same time as I installed Nagios!
Issue closed.