I wish I knew ...

Judging from Paul Nesbit's message above, it may be a matter of the base install version.
When I was having problems, I was using an Intel 100B and 3Com 900B for NICs. I swapped the 3Com for another Intel and re-installed.
When it got to the initial setup screen, I switched to another teminal (Alt-F2) and installed the updated mailx rpm, the 4.0.12-28 base rpm (I thought it was the most up to date at the time), and the PPPOE rpms.
I then configured it exactly as Charlie said: set up for dial-up, entering my DSL login info, and rebooted. After reboot, I set up for dedicated DHCP and rebooted. When it came back up it logged in just fine!
I hope this helps.
Cheers,
.....G