Does the modem get IP though? If it is provisioned, it should work. I have similar issues about every other month with Charter on a 3100. It is usually a sign that the #$@* Cisco router they use is screwing up again. Not sure if they reset that switch or what they do to correct it though. If you are getting IP, check your lease length. It may be a sign that the switch is having issues and not the surfboard.
I think I finally have enough customer history (I talk to them every month now) that they start to believe me. I did have to ask for the supervisor immediately last time though because the "tech" support person wanted me to reboot my OS because the surfboard was not getting time of day or IP.