Internet disconnecting every 6 hours or so.

Yesterday evening around midnight. I noticed that my internet connection was not working. I checked my motorola sb6121 modem and I noticed that the 2nd and 3rd lights were off and the 4th light was blinking which I believe was the data light. So I unplugged everything. I powercycled my modem and router. I was able to go online again. When I woke up the following day. I noticed on my airport utility that I have no internet connection. All the lights in my modem were there. I did a direct connection. I get an ip address that starts 169 when I hooked up my mac directly to the modem via ethernet. So I call cox and asked the Tech Support agent to reboot or restart the modem. I told her that I have an airport extreme for my router. She told me that I should disable ipv6 sharing. Does IPV6 sharing have something to do with this. I had that checked ever since I got this router a year ago. So I don't believe that's the cause of the problem.