Cable modem wasn’t responding.
I did the usual unplug-the-modem-unplug-the-airport two-step but still no joy.
I called Comcast and found out they disconnected my service 5 days before they were supposed to. At least they admitted it was their mistake, but they will not send anyone out to fix it.
Thank god for WirelessModem and my kind neighbor who is going to set up his AirPort with his newly installed DSL line and allow us to share his bandwidth this weekend.