I've started getting a resolution not supported on my roku also. It will work fine with hulu and then I try to switch to Netflix and it shuts done with that message. It will also cut out sometimes. It looks like flashes of color or no sound. I would think it was my tv but it only happens when using the roku
What model Roku do you have? The older devices are beginning to become unsupported, and channel support isn't available any longer.