For those who replaced their videos encoded with XviD codec or other custom settings and the videos are no playing back properly,
make sure you use the following options :
Resolution : 320x224 (AR:1.429)
Fps : 15
Interleave : 15ms
Keyframe : 1 Frame (-> every frame)
Fields : Full Frame
Request Data Rate : None
Still Optimize : On
(some of these options only exist in Adobe Premier)
I hope that was somehow useful to someone... >.>