I'm not sure of RH8, but FC2 keeps all it's network devices (connections) in two locations:
You might want to set it up manually, so try this:
# cd /etc/sysconfig/networking/devices
See if a file called ifcfg-eth0 is listed. Just remember if it wasn't:
# vim ifcfg-eth0
I use Comcast also, so yours should probably look like mine also. See if all your settings look like this:
Press escape and then :wq to save and quit out of vim.
if you didn't have a ifcfg-eth0 file in the directory, you need to do this:
# cd /etc/sysconfig/network-scripts
# ln /etc/sysconfig/networking/devices/ifcfg-eth0
I use a router and a D-Link DWL-G520, so if you're connecting directly to your cable modem, you may need to set up some stuff, which I think you can do through the GUI.