720P video blacking out every few minutes

Hi, every few minutes watching a 720P h.264 MKV with AC3 audio the following happens

-screen blacks out
-TV displays reslution (through its own gui rather than XBMC), screen is still black
-video comes back a few seconds later
-audio comes back a couple seconds later

Here is part of my log, I am running Raspbmc RC5

http://pastebin.com/ZmtBKre4