Does "No such device"->grub rescue on on an established system herald a catastrophic event?

I've already found plenty of threads on "no such device" and grub rescue on AskUbuntu, but I'm wondering what this signifies if it happens not on a fresh install, but on a computer that has been behaving normally for well over a year.

Is this a sign of catastrophic hard drive failure, or possibly another issue? Or is it a just-happens kind of thing that crops up from time to time with Ubuntu?