Why can't I telnet into my Linux box as root?
By default, some distributions prohibit root from logging in remotely, unless you first log in as a regular user, and then "su" to root. This feature provides an extra layer of security in case the password of the root account is compromised.
Although it is not recommended, this restriction can be removed by deleting the file /etc/securetty. For more information, type "man securetty".