Does anyone know what that was about though?
Well, it's Windows Vista. At this point, I think we can all safely say that even VISTA has no idea what it was about.
My guess is, though, it was probably something to do with the Vista Boot Manager, which does NOT like being contested for its position, or it was something to do with the partition shrinking, and Vista questioning why. Probably nothing you didn't know already.
"People should better think of their computing devices as facilities lended by the DHS." -Berke Durak, Linux wipe (secure file deletion) development.