Well there I was, rebuilding a router and having a good time when I accidentally damaged the partition table on my main Linux installation, which is a GUID partition table, or GPT.
How did this happen? I was installing Voyage Linux on a compact flash card, and while I was messing around with GParted and other filesystem tools I accidentally ran some commands on/dev/sdb, my main hard disk, instead of /dev/sdc, the compact flash card. Like, oops. I don't know exactly which operations gummed up /dev/sdb, which would be good to know.