This is likely more to do with the playback device than the TV. Here are the differences in the devices you have reported that I can think of:
- Your plazma TV (problem)
- No playback device was mentioned so it is very possible that it is interlaced playback
- Your son's portable (no problem)
- This would likely be a modern DVD player with LCD output
- This device is likely to be capable of playing progressive
- Your friends CRT TV (problem)
- This would almost certainly be interlaced playback
- Your son's PS3 and Plazma (no problem)
- The PS3 will prefer progressive playback if the TV supports it and will automatically upscale
I suggest you open the source AVIs and the edited AVIs in Gspot to see what they are:
http://www.videohelp.com/tools/GSpot
Specifically, what is important to report back is "Pics/s", "Frames/s", and any of the little boxes that are lit up just below them.