Similar problem here...
I have 3 comps plugged into a hub, which goes to a DSL modem. All 3 machines have a working LAN set up in XP, and all have working pppoe connections.
In Redhat though, the same options don't seem to work. Linux finds my sis900 adapter, and it also shows that it's working fine. Then, when I set up an xdsl connection through eth0, it fails to initialize ppp0. I don't have DHCP, since I connect through teh hub straight into the modem, and have a dynamic IP with my ISP.
I am a newbie to Linux, but my fairly experienced friend sat at my comp for 3 hrs as well, and couldn't get it working. Any ideas?
Thanks.