I have had Comcast for a couple years now, I recently moved to a new residence and I transferred my service. Comcast advised that I needed a new modem with docsis 3.0 in order to get the fastest speeds. I WAS using a motorola sb5101 modem and a Netgear wireless router WNDR3400-100NAS N600, and I never had connection issues.
Comcast sent out a UBEE ddm3513 modem, and I continued to use my wireless router. I got everything setup just fine, I had a laptop and a desktop which both connect wirelessly. I started to notice though the connection would just drop and then reconnect, I knew this because my desktop PC would make a noise on a successful connect. I watched the desktop and when it lost connection I checked the laptop and it was also disconnected. The lights on both the router and the modem were all lit up as if everything was fine. I ended up hooking the laptop up to the modem via ethernet cable and the connection was fine.
Figured it was the router since I have had it for a couple years and was wanting a new one anyways. I bought a Netgear WNDR3700v4, hooked it all up again and I am still having the connection issues. Any ideas on what else to check? I also changed the wireless on the router from auto to channel 6.
Update: Well, I stayed connected long enough to look at the logs in the router, noticed DOS attack, that can't be good...screenshot at the top