I’m happy. I have discovered WHY the avi files created with VisualHub and Handbrake (with XVID codec) cannot be played by my table DVD player (look my old post for more infos).
The AVI container created by these two programs are not compatible with my DVD player and the resulting video freezes/trigger and jumps continuously.
By CHANCE I converted a file and then used VirtualDub to do a DIRECT pass-through of both audio and video parts (loss-less). The target file was 1MB smaller in size. Why? I have decided to test it and, surprisingly, it played smoothly in my table DVD player. These videos are now played perfectly!
Alleluja! Now I can use the multicore power of HandBrake for my encodes (the only OSX program that REALLY uses it!).
Same video source and conversion parameters.
Avidemux : 8fps.
Handbrake : 30 fps!
No frames dropped on all recent projects (good but I don’t know why, maybe osx updates changed something), fixed video size limitations always present but I’m overcoming it.
I hope that coders will update Handbrake with the latest xvidcore as soon as possible and remove these video limitations 
