Boy, what an idiot I am. I was testing a new 2.6.18 kernel build on my home machine, which was having some dhcp networking issues, and entered a static ip address in my house’s private network 192.168.2.x address space, only to realize twelve hours later I had been typing through my ssh connection to the server. Fortunately, my server is a virtual one, and was easily reset once I had learned of its state — it took another twenty minutes digging through log files until I discovered the cause. Oops.