So anyways, I have a 17" intel core 2 duo iMac (white one, Upgraded to 10.5) My Itunes library works really well on this computer, MPGS run smoothly on it. Issue comes when I try to playback an mpg video from quicktime or from itunes on my MBair of Mbpro.... The video playback starts flickering and looks as if it was being streamed from a very slow internet connection.... I thought It was a software issue because my imac was working fine, so I restored my MBA (swiped hdd and fresh install) and copied ONLY an mpg file to the MBA and same issue again!!!! .movs play seamlessly on all 3 computers, its mpgs that are giving me a hard time! Any help or suggestion? thanks!