I have a Sony AVCHD HDD SR7 with 60gig on board. I also have a white iMAC 2.16 ghx core 2 duo with 1.5 gig ram. I am using Voltaic to convert the AVCHD files to .mov files where I use Quicktime to view. I plan on using FCE 3.5 to edit my video. When i convert using Voltaic any file that is converted to a size greater than 4 gigs does not play back properly. The audio plays fine, however, the video jumps frames and sometimes just freezes on a frame while the audio continues along. All files that are converted to a size smaller than 4gigs play back perfectly for audio and video. I am converting to 1440 x 1080. If i convert the AVCHD clips to a lower resolution (720 from 1080) and the file converts to a size smaller than 4 gigs the converted file plays back properly. I have taken one of the larger than 4 gig converted files and created a DVD using iDVD to see if it would work but I still have the same problem. I have called Apple Care with no success and another forum where I was told to upgrade to Quicktime Pro and more RAM. I really dont want to spend more money if I dont have to. I can't understand the 4 gig barrier. Can anyone assist?