If you've already tried power cycling the boxes then it's likely a hardware issue. You need to contact Telus customer service to get replacements.
Spontaneous reboots sometimes are a sign that the boxes are overheating. Do you have the boxes in a cabinet or stacked on other electronics?
Our main box (which fails sporadically while watching live tv/PVR) is on a wire shelf, nothing around it, ample air flow. It was just replaced by Telus within the last year as the PVR failed on our last one.
I think I'll be getting in touch with Telus to have everything replaced.