I am having an issue that recently started and maybe someone can point me in the right direction. For the last month or so I can no longer watch movies that are .MKV on any application. I was using XBMC, Boxee, PLEX, VLC etc and all of them did work at one point and time but recently my macbook pro connected to my HD TV via DMI to HDMI will not play the movies properly. The movies will either play choppy where they are off from the sound and video when using XBMC, Boxee or Plex. When using VLC they are pixelated the whole time really hard to see anything. I had taken my laptop to the apple store to have the CD/DVD drive replaced and mentioned this to them to which they said they did not find anything wrong. I was thinking maybe it was graphics card related. So the genius there told me to reinstall the OS and to only use "Apple supported" files/movies. So i did reinstall Snow Leopard on the machine but the problem still continues. I have tested it by using shows/movies in M4V format from apple playing it through Itunes and have not seen the issue with the video. Anyone have any ideas of what it could be that caused/is causing this issue? Any help would be greatly appreciated. I am running a 2008 17" macbook pro w/a 2.4 GHz, 4GB RAM, 160 GB HD, OS is 10.6.4 with all the latest updates. All my movies are housed in my 2TB external HD "My Book" but also i have tried to transfer them directly to my macbook pro HD which does nothing to correct the issue.