I am getting constant reboots and power cycles from the modem, quite randomly.
Noise Margins are 8dB (down) 16dB (up), Uncancelled Echo is 1.8dB (yet I don't have ANYTHING plugged into a phone jack in the house other than the modem). Using inSSIDer I see I am the only one in my area broadcasting on channel 11 (next closest is 4, most everyone is on 1).
The noise margin of 8 is about the minimum you want, but it should be ok as long as it isn't dropping lower. The "Uncancelled Echo is 1.8dB" is worrisome and something I believe you need to address. How long has this been going on? What changed?
One way to troubleshoot this is to put the 2wire at the NIC; bypassing the house wiring and see what the readings show.