I've been trying to upload some videos for editing that I shot from a GoPro 3+ (MP4).  When I try to play the videos MM only plays a black screen with no sound for the duration of the video clips.  At the bottom where is says that MM is preparing my videos, the bar is 100 complete, but it never seems to totally prep the clips.  I've tried with several clips ranging in length from 1 second to 5 minutes and they all yield the same result.  I've kept the program running while I was away at work and still no progress upon arriving back at home.  Am I doing something wrong?  The program can't take 8 hours to prep a video clip, can it?