I have exactly the same problem. The clips looped ok when played in QT player. I'm using OSX10.4.9, Modul 8 2.5.4, QuickTimePro 7.1.6 on a 2.16GHz IntelCore 2Duo iMac with 2GB Ram, 256MB graphic and runs the clips on the internal 7200rpm hard disk. hope someone will have a solution for this problem....