Seen other routers have issues with this cable modem. This modem seems to be a router/VoIP and internet modem.
I would try to put the 655 router into the cable modems DMZ if it has that option and see how that works.
I'm not sure how to go about that...
I also have been having trouble trying to port forward so I can set up a minecraft server but it hasn't been successful.
I will try to do some research later.
Here is the info about the modem from the Arris website:
http://www.arrisi.com/product_catalog/listers/index.asp?id=385
My previous router was a D-Link DIR-615 and I didn't have any problems with it until a couple months ago when the router kept disconnecting.