Video image and sound doesn't sync in fullscreen mode

Hi, I’m playing a avi format video using vvvv,
and it works fine on one machine, and i then copy the v4p file to another, all the node are the same, but in new machine, the video plays well in small render window, but when it goes fullscreen, the sound seems all right, but the graphics doesn’t, it looks a little bit slow, and can’t sync with the audio.

does any one has the same problem??
by the way, my two computers have the same cpu and gpu and etc.