XBMCbuntu crashing on hd mkvs

Ive set up a new system.. the fastest xbmc setup in the house.

My xbmc system crashes when I play any high def content. This leads me to believe its a video card issue but the card in question is a nVidia Geforce 9600 GT, The cpu is a intel dual core 2.8. I have way crappier systems that handle hd fine.

here's a pastie but as soon as the video comes up it stutters for 20 sec then reboots.


http://pastebin.com/gGc8Aqt6

I'm betting this is something stupid and my low level of linux knowledge is to blame.

Any suggestions are appreciated