Have to repeatedly reboot my Airport after upgrading modem to Cisco DPQ3212

Since moving and having cable-phone modem installed by Cox, I have found that my Airport stops working anywhere from 1 to 12 hours later. Phone service is NOT disrupted. If I directly connect my MacBook Air to the cable-phone modem, I am consistently on line (3 days). Today, I have been using the laptop for several hours and I find that I had to disconnect A/C power from the Airport and reconnect four times since noon! According the the Airport utility app, I have the latest version of Firmware (7.7.3). Anyone have any suggestions?

Thanks,

Henry