Ok, I think I've tracked it down to the IR Repeater I'm using. I have a Sanus ELM 501. When I unplug it the ROKU works fine as long as I have line of sight to the ROKU's IR receiver. If I plug the IR repeater back in to turn it on, then the problem recurs. So its something about the IR repeater that's affecting the ROKU. Any ideas on this? Thanks.
Its putting out IR junk signals that are bombarding IR of the roku. find an old x10 key fob and RF transceiver set, use it to turn on & off the IR repeater. You use the IR repeater to control it from different room? Leave it on when afar, when close turn off the x10 it like unplugging from the wall.