I have three Netgear Routers: WNDR3700, WNDR4000, and WNDR4500.
On the SAME wired network, the 3700 works great. But both the 4000 and 4500 exhibit the same symptom. They periodically drop WAN connections for a minute (almost exactly), then allow them for 5-20 seconds, drop them for another minute, etc. In the plots below, red in the time graphs means that traceroutes and pings are not getting returned by the affected hops along the path (top part of the plots).