In this case since there is no WIFI you can restart the modem and check for WIFI connection if still no WIFI you need to perform hard reset on the modem after resetting the modem will go to default setup any custom settings will be removed so use the default network name and password to connect to your network. so after connecting to the WIFI network you can change the WIFI channel on the modem interface to avoid intermittent drop outs. Please follow the steps mentioned on the below article to change the WIFI channel and resetting modem

http://arris.force.com/consumers/articles/General_FAQs/SBG10-Factory-Reset

http://arris.force.com/consumers/articles/General_FAQs/SBG10-Changing-the-Wi-Fi-Channel.

Turned out to be a defect modem.  I just received the replacement modem last night, and put it on.  This morning it already started having intermittent disconnects, which kicked me out of a meeting.  Is that normal behavior?  

BTW, during the 2 weeks I was waiting for the replacement modem, I bought netgear nighthawk cable modem router, never had any problem.

If you are experiencing with intermittent internet connection, I suggest you to change the Wi-Fi channels and also check the cable signals to make sure all the signals are in range.

Let me help you with the link:

http://arris.force.com/consumers/articles/General_FAQs/SBG10-Changing-the-Wi-Fi-Channel

http://arris.force.com/consumers/articles/General_FAQs/SBG10-Cable-Signal-Levels