Well, here's what I tried this evening. I set the Video Performance to low and unchecked the "Always Process the Entire Media File" option (actually was already unchecked from trying to figure things out last night). I loaded the channel, went to the CW, selected a video (ANTM which I SO don't watch, but in the interest of this experiment, I just picked one), let it complete the initial "loading," then hit the pause button. I left it on pause for about 5 minutes, started playing the video and was able to watch 20 whole minutes (that's as long as I could tolerate those folks) without a single loading/replaying episode. Then I went to TV-Links, selected the most recent episode of NCIS, did left it on pause for 4-5 minutes at the beginning, then proceeded to watch the entire episode with only 1 load/restart episode. When that episode occurred, I went to my computer where there was a message on the screen about an upgrade for my antivirus software. I closed out that message, went back to my show, and watched to the end without further incident. I feel like I'm on the cusp of discovering, but I just don't know what it is. Was it the "low" video setting, the "don't always process the entire file," the pausing at the beginning to let things catch up with one another (for lack of a better phrase), or just dumb luck? Sorry to ramble on, especially since I don't really know how all this works, but any suggestions would be most appreciated, as I really, really want to keep the Roku if I can get it to play nice with PlayOn, or vice versa. Thanks for listening to my nonsense.
Based on the fact that you can pause the show, then come back and watch uninterrupted for a period of time, the weakspot seems to be your computer. It does not seem to be able to transcode to an HLS stream to work in "real-time".
When you say "set the Video Performance to low" do you mean in the PlayOn Windows program? Did you try and change the stream quality setting within the Roku Channel Settings on your TV? As I mentioned before, I'm not sure whether the settings in the PlayOn program impact the HLS streams that the roku is using. I do know I can select between 2 streams (High/iPad or Low/Iphone) when browsing the content. I'm not sure how much less CPU the lower quality stream uses, but in theory it should help.