I'm having a similar problem. My digital box stopped responding to the remote control. The model is DCX-3400M. So my SHAW remote works to turn on the TV, control the volume, etc. but can't control the digital box.
I've changed the batteries in the remote, as well as tried the two things Colin suggested (resetting the digital box and changing the channel on the digital box while the TV is off). Both of these had no effect.
What can I try next?