Root login fails when using serial dialup modem

[Bill Jones]

I'm trying to help someone configure their filesystems using remote
dialup but the root user login fails when I try to login after the modem
answers and provides the login prompt. I have ttyS0 in the
/etc/securetty file. RHEL 4 is the s/w version in question.  It says
invalid login when I attempt root login. The same login and p/w works
from the system console. Does anyone have ideas what is causing the
login to fail?

Thanks,
Bill