Sharing An Internet Connection


I used to be able to share and Internet connection from my 10.4 running G4 and the other computers on my small home network, now I'm not able to do this, I'm not sure when it stopped. I can ping the g4 from any other computer on the network and any other computer can be pinged from the g4. I can share files and so on the only thing that really seems to be having a problem is the sharing of the Internet connection. here are the details about the connection, I'm dialing up with an internal modem using ppp. I've set the Internet sharing to on over the Ethernet connection. Any Ideas?