While attempting to edit clips on the timeline, the preview window does not keep up with the video at all, all of a sudden. When cutting or triming it now takes ridiculously long and has a "not responsive" note in the nav bar until it catches up. These are .mov files of less than 8 minutes in length and it's dragging out a project that should've been done a long time ago. I'm on a laptop with AMD Raedon R4 gpx, 8gb RAM, nearly 1tb disc space, 64 bit processing, Windows 8.1. Any help?