I switched my DNS IP to 126.96.36.199 a few weeks ago to see if that was the problem, but no luck. IPs are not that close. I did notice that when my internet goes down for a few seconds, my ping time to the router is >500ms even though I'm wired. I'll call comcast to see if something isn't playing nice. Maybe just need to power cycle it or have comcast send a reset signal. Thanks for the help!
Besides the XR1000, I'm using a netgear CM700 as my modem, so there is no comcast hardware. Only thing I can think of that I recently added to the network is a SimpliSafe home security system (base station, cameras, window/door sensors, etc).