Mac OS X Blocky colors

ok guys, i got m hands on a mac mini and installed xbmc on it.
I have an issue with SOME videos.

Not really pixelization, but more like "color blocks". Like some parts of the video dont blend in and get blocky and sometimes even very distorted.
I am loading the video directly from the mac HDD.

I did however test multiple videos and not all of them have this issue.

2 perfect examples:

Working:
Naruto Shippuden - encoded by Hatsuyuki fansubs
Video: MPEG4 Video (H264) 1280x720 23.98fps [Video]
Audio: AAC 48000Hz stereo [Audio]
Subtitle: Advanced SubStation Alpha [Subtitle]
mkv container.

All blocky and stuff:
Fate/Zero - encoded by UTW
Video: MPEG4 Video (H264) 1280x720 23.98fps [Video]
Audio: AAC 48000Hz stereo [Audio]
Subtitle: Advanced SubStation Alpha [Subtitle]

I dont know what could be the issue, but I could only guess the way they were encoded.
Do macs have video codecs that could be updated like windows?

Both videos play perfectly on my windows laptop and show perfectly when my laptop is connected to my TV via HDMI.

edit:
Sorry guys, i cross posted. It wont let me delete the other post in general

This is a Hi10P issue. XBMC v11 doesn't have Hi10P support, but nightly builds and monthly builds do. If you use one of those then those files will playback just fine. The latest monthly build seems stable enough for day to day use.

oh really?
how can i figure out if its encoded with Hi10P?

MediaInfo will tell you. Some groups are nice enough to label their files, too. Some are jerks about it and feel everyone should just upgrade their player, despite Hi10P being considered non-standard for consumer video playback. Lots of players still aren't updated for it, and anything that requires hardware decoding won't be able to play them back correctly. Most desktop CPUs from the last few years should be more than enough to play back Hi10P, though.

thanks ned!

(2012-06-18 01:57)Ned Scott Wrote:  This is a Hi10P issue. XBMC v11 doesn't have Hi10P support, but nightly builds and monthly builds do. If you use one of those then those files will playback just fine. The latest monthly build seems stable enough for day to day use.

I have a stupid question (like I ever posted a smart one

I've seen the announcement about starting with monthly builds a while ago and thought it a good idea. Yet, when you go to downloads they are nowhere to be found. Furthermore, they are news about them being available on home page but again the links to download those monthly builds are missing. It would make more sense to me if the nightly builds are buried not the other way around.

http://mirrors.xbmc.org/snapshots/

as mentioned in the monthly build link.