So here's my issue. I can load video into iMovie and edit no problem. After about an hour or so the preview box will randomly stop displaying. I can then only view in full screen. On some occasions it wont allow playback at all. Sometimes a restart works but most of the time I just have to try every few hours until it works again. Anyone have any clues? I searched but havent found a clear answer/resolution. One last thing, I have been able to complete videos in the past. This has gotten progressively worse over the past few weeks. Thanks in advance.