My first question is who are you trying to ping?
You probably know what you are doing, but just in case
are you trying a site that does accept ping?
I used to use netscape but seeing as that doesn't work anymore,
now I use ping www.freshmeat.org
<quote>The external nic is connected to a linksys router and is getting the IP via DHCP from the linksys device. </quote>
If that is working, this is all I can suggest.
Oh yes, and those iptables. New to me too. Just ran in to it recently.
Never really bothered about it before...