Cannot play MKV files in XBMC

Hi, I have ATV Flash installed on my Apple TV. When trying to play MKV files through XBMC, I get an error saying that XBMC/Boxee has exited after 10 seconds. This message appears after the Apple logo has been shown and XBMC has exited. Any idea how to make MKV files play on my Apple TV? Thanks in advance, Simon B. Støvring

 Do you know the specs for you MKV files? Do you have a Crystal HD video card installed?