I'm having this exact same problem on my older MacBook. Playback starts fine, at random points throughout, video playback freezes, audio continues for a while, then stops. After a few seconds, both audio and video playback resume, but video runs fast to catch up to the audio. This only seems to happen on HD video files.
This has been happening for the past month or two on 10.1, but I was hoping the 11.0 RC would fix it. Before that, though, it's been fine.
Here's a log:
http://pastebin.com/u4UFANpb
This freeze-and-catch-up happened three times during the playback of a video in that session.
Hardware: MacBook MA700xx/A (Late 2006) (2GB RAM)
OS: 10.6.8 (10K549)
XBMC version: 11.0-RC1 Git:20120226-30312f1 (Compiled: Feb 27 2012)
And here's the mediainfo for the file I was playing:
http://pastebin.com/3jaUkDZN
Really hoping this can get worked out. It's a real pain having stuff freeze in the middle of watching it. Let me know if there's any other info I can supply.