I just bought my new 17" uMBP, and figured it would have no problem playing 1080p movies. I was using the 9400 chip, and it was choppy at times. Then I switched to the 9600GT chip, and it was the same thing. I even restarted the machine. I was trying to figure it out. Maybe it was the file itself, even though the type of artifacts, I have never seen with MKV, other than occasionally on my old underpowered CD 1st gen black macbook struggling to play high quality 720p. So, I decided to watch my istats while I was watching the movie, and every time an error occurred, my HDD read peaked, and I guess totally maxed out. I have the standard 500GB, 5400rpm drive. Can I really not watch 1080p movies because of my HDD?