I'm not certain... the Linux box is on a UPS, along with the DSL modem. I think I hung the ethernet switch on it too, because I can ping my iBook, but nothing else in the house answers.
Yup, the power was out. As I wrote this, a ping went through to isn2, the MythTV box. I ssh in and it reports 7 minutes of uptime. My APC UPS saves the day again.