I have been putting clips on face book via you-tube. I have hit a snag trying to combine two clips in windows movie maker. the video stops and the music continues. It stops at about 47 seconds. I can play both segments separately but they will not play when combined. the intro clip is 17 seconds long and that means that the main clip plays for about 20 seconds and then the screen goes black. The combined clips have a 4:30 duration.