Are you sure it's actually turning off?
I'm running a very similar set up.
I've had problems with the receiver not connecting (allways my fault) but it never turns off. It will usually show the ip address of the server it was trying to connect to along with the subnet mask abd the gateway ip address. The screen might go blank, but if you press the menu button you should see the error message. Also, try UNPLUGGING the DAR. It seems to do more of a full reset (for lack of better terminology)