DNS Woes

[stucklenp at charter.net]

I have a challenge: since running "yum update" and blindly  accepting all the packages and then rebooting, I have not been able to get my Fedora box on the Web.  Since that system is my firewall box it is really important that I get it running again. Note that I get the same symptoms with or without the firewall running.

The NIC is configured to "Automatically obtain IP address settings with DHCP" and "Automatically obtain DNS information from provider" (I have tried manually setting DNS addresses as well.)

When the network service is started, the NIC does get a valid IP from the ISP, as verified by the ISP.  As well, I see the lease information in the messages log.
"...dhclient: bound to <myIP> -- renual in 13961 seconds...
ifup: done... 
network: Bringing up interface etho: succeeded"
 

Other Symptoms: 
ping <external IP> results in "Destination port Unreachable."
ping <leased IP> Works fine.

Redhat Network Configuration show the NIC active and "ok"
resolve.conf contains the correct IPs for the ISP's DNS servers.

To add insult to injury, when I plug my Windoze box into the cable modem and set its IP to use DHCP, I have no problem attaching to the Web. 

Any ideas as to how I can resolve this?

Thanks