> Was this the second time you booted the machine, or a different?
This machine has been booted a couple of times already and it usually comes up without an error.
> The bit about installing updates intrigues me, you're saying that updates result in this happening on the next reboot?
Exactly. It doesn't seem to be coupled to any particular package or something like this.
Last time there was only one single update (https://lists.ubuntu.com/archives/karmic-changes/2009-October/010704.html). After update-manager was finished, I rebooted the machine with the fusa and got the error I posted above.
I did some more tests and interestingly the error appears on the first _reboot_ after an update. It seems as if there can be any number of shut down/start up cycles inbetween - those won't trigger the error. I tested different variants of that a couple of times and it seems to be reproducible.
By the way, it doesn't matter if I have the VirtualBox guest additions installed or not. But I could also try this out on a physical box if that helps.