I also posted this in the other dm800 hang topic. might be usefull:
My DM800 also hangs after about 10 minutes of watching HD channels.
Seems te be heating problemen. I tested it simple by putting my box on it's side ( with the oled screen upwards ) and this seems te give it just enough cooling to not stop working. Watched BBC HD for more than 2 hours and it still worked. Left it on all night and in the morning it was still working.
Just to let you know an perhaps some people with the same problem can test this also. ?
Altough putting the dm800 on it's side it is not a real solution ofcourse 