Lesson for the day
When somebody provides you with a password for a system, sit down with them and make sure that it works. Especially if they're going away for six weeks. Don't just ask if they're sure that's the correct one, have them watch you as they try it.

Better still, install ssh keys on the machine once you have access.

I have a client who's been handed to me, and my first experience with them has been "Oh dear, that password doesn't work. I don't have access to your system."

We do have physical access to the machine, so if we need to it may be possible to boot the machine from CD and directly change /etc/shadow. I really don't want to be doing that, especially given that root lives on a linux software RAID-5 drive, and I have no idea if my regular recovery tools will mount that without complaint.

The good news is that a person who may know the password will be back on Monday. Let's hope that solves things.