I've had videos takin off my old pc and put onto my mac that i know are 20 mins or so long but won't play back the full clip on my mac for some reason (only about 2 minutes of the start). When clip reaches the end if i drag back the playhead however other bits that weren't shown start playing. Just wandering if anyone can help? maybe there is a setting i'm not using or something? Thanks for ya time. James.