AsusDave--
Thanks very much for helping me.
Roku's site is not helpful, nor have I gotten any help from the community boards.
I did get lots of help from the boards at
http://forum1.netgear.com/
What initially worked for me was to go to the router's control pages and see where the roku was showing up. From there in the router's control pages I set up a static route to the roku. That got it working. I thought fine.
A couple days later Roku tech support finally answered my email and said that A. the thing to do was to reboot all three: cable modem, router, and roku; and B. there was no way to set up a static ip on the roku.
I experimented and first disabled and then completely removed the static route. Still the roku works.
Theory: when I set up the static route, the router goes through some magic process that takes about a minute. That might be the equivalent of rebooting the router. Someplace in all this I did reboot the cable modem. And of course I was constantly rebooting the roku.
So I suspect their method worked--simply reboot everything. Sounds like the Windows way, huh?
Thanks for helping me, Dave!