Corrupted password file

I first bought hosting back in 2000 I think. On the recommendation of a friend, I chose Nexpoint, and bought their shared server package which was based on a Cobalt RAQ server. This has worked fine ever since, and on the few occasions that I've needed support (password reset and PHP reconfiguration) they have been helpful and efficient. On Wednesday I thought I'd try to upload the howbigismypotato files to my webspace, to try it out as a possible hosting option. I couldn't log in through FTP or SSH using any user I could remember, so with a sigh I submitted a support request to have the passwords reset. I was surprised to get this message in response:

The password file on your server has recently been corrupted. The server you are on is a cobalt linux server and cobalt no longer provides support for their servers.

Oh dear. How often does this sort of thing happen? I've never heard of it happening at work. It must be quite a nightmare in a shared hosting environment like the one nexpoint run. Amusingly all my web pages, including the dynamic stuff, was still working fine without me having looked at it for years. If I'd never tried to log in at the host level, I would never have known there was a problem.
Thankfully Nexpoint provided a good solution - moving all my files onto a newer server, and effectively setting me up a whole new hosting package. It all went through smoothly and I remain very happy with their service. Now it's time to get on with something more productive.