try as cactikid states,have you checked how much memory you have when box is running in information I would also try to record onto usb playback to see what happens.
The only time I have experienced anything very similar is when I flashed a new boot loader and got a bad flash I just re-flashed the boot loader and all was ok. just something for you to consider as they may have done the same.
personally I would go back to the beginning remove hard drive flash boot loader flash image load all settings you want once that's working then install hard drive, if you have problems after that I would return the box as faulty.
my m8 has this box and has never had any problems have you had the cover off and checked all internal connection's.