Perhaps your Centos machine has a statically set IP address that conflicts with some other critical piece of hardware, such as your gateway or router?
You could troubleshoot this as follows:
On some other Linux machine that's capable of accessing the internet, check to see what its default route is:
sudo route |grep -E '(Gateway|default)'
The line of output which begins with default should list an IP address immediately following the word default - this is probably the IP address of your gateway or router.
Check to make sure that your Centos machine isn't configured to use the same address by connecting it to the network and then checking its IP address(es) with
ifconfig -a |grep -B1 'inet addr'
If any of those addresses match that of your router, that is likely the source of your problem. Change the IP address of your server to something else like
ifconfig eth0 down && ifconfig eth0 192.168.1.199 netmask 255.255.255.0 up
If that works, you can make that IP address change permanent by editing