I'm confused and getting frustrated here. So I got one of the new base model 15" MacBook Pro's today, and everything has been mostly great, except some issues I've been having with video playback iTunes. Before this, I was on a 2007 C2D MacBook, and iTunes performed like a champ on it (despite the obvious hardware difference). However, I've been having problems with video playback on the same version of iTunes (10.2.1) on my new MacBook Pro that I didn't have on the MacBook. Namely, scenes on the videos I play in iTunes on the new MBP get incredibly pixelated/blocky once in a while so movies become unwatchable. The same scenes play completely fine on the older MacBook in iTunes. The movies play identically in Quicktime X Player (there's some pixelation there, too, but at least it's the same between the two, and I chalk it up to the immaturity of its libraries vs. QT 7.) And both play perfectly in MPlayer on both machines. But iTunes behaves completely differently when playing them back. What is iTunes doing differently between these two computers? They're both on 10.2.1. The movies are all H.264 high profile w/ AAC audio in an mp4. Also the subtitle positioning is a bit wonky in iTunes on the new MBP where it's fine on the older MacBook. Does anyone have any ideas? Anyone else having similar video problems with iTunes? ETA: Ahh, after an hour or two of trying to figure this out, I decide to post, and then five minutes after I post, I finally solve it. I just tried re-muxing the video and audio streams from the old mp4 into a new mp4 with Subler on the new MBP and it plays fine, now. No idea exactly why that worked since the same file plays fine on iTunes on the MB and plays identically in all other players, but whatever... It's going to be a pain if I have to remux all my TV shows again, too... ETA2: Urghh. Nevermind, this only seems to work for some of the movies. For others it still leaves messed up playback.