I have had this problem for quite some time. I have a mid 2009 MBP with a 2.53GHZ processor and 4GB ram. Should be more than enough to handle what I do, internet, watching videos purchased in iTunes and iPhone/iPod related tasks. The only problem I have is with watching videos. The videos stutter and most times it is 45 seconds before I even see the video on the screen. I move the slider back to the beginning and it plays fine. The next video I click on plays almost perfectly. The videos are stored on either a LaCie enclosure with two WD 1TB drives and an enclosure bought at Microcenter that contains two WD 1TB drives. The LaCie is attached via firewire and the other drive via a USB port. Once I do something else on the computer for awhile and go back and watch a video, the same thing happens. On Sunday, I purchased a used black MacBook with a 2.4GHZ processor and 4GB ram. If I watch a video on this MB using sharing in iTunes so that I watch the videos through the MBP, the videos start up perfectly with no stuttering whatsoever. I have no clue why. Anyone know whats happening here and why the videos stutter on the MBP. Both computers are up to date on software. Thanks Edit: I have a completely restored copy of the OS with no apps or data on it at all on another drive. I am thinking of installing it and trying to add some videos to it but keeping them on the externals as a test to see if it too has the problems.