One of my development virtual machines went belly up after a recent system upgrade. After tinkering around at the grub> prompt to no avail, I booted a LiveCD, followed the instructions here: http://sazeit.com/articles/repair-or-reinstall-grub-with-boot-repair, and was up and running in minutes. Moral of the story; sometimes it’s more important to solve the problem than understand the underlying issues…not often, but sometimes :).