OK, I re-converted the video I had problems with using the Media Converter for 770/n800 and converted it to n800 Super High Quality 800x480 and then used MPlayer r15 to play it. It played fine. One little hiccup where the video froze and the audio was still playing. I paused and played it again and the video caught up and it did not seem to happen again. I re-played the video to that same spot and the video played fine with no video freeze the second time. So looks like MPlayer r15 is working fine in my n800.