Wait... Are root logins allowed (by the existing, possibly the install default,
configuration) ? have you ever logged in as root from a serial port? I would
assume that a collocated box would be setup to allow this, but it may have been

Can you SSH to it from the outside and sudo/su to change the configuration
and allow for ttySN (serial TTY) root logins? That is likely your problem.

You can get to the disk(s) from the installation process of any distro, and
I prefer Slackware (of course) for such hacking.

One more relevant but not helpful note regarding this last part. Typically
we impose BIOS passwords and use crypto MD encrypted containers for systems
that are out of our hands (collocated). This out of sheer paranoia. You should
do that when all said and done, but never take my advise.

Man! This system has given you some trouble lately.