Still haven't gotten anywhere w/ this... the issue presented itself today.
Using the hidden "D" menu, I surfed around the diagnostics and saw that the EDID modes for 1080p were correctly reported while the box was outputting HD channels in 480p... while the issue was present.
This leads me to believe the problem is the box and not the TV, but I'm really not sure.
How can I get anyone at Verizon support to understand this? Is there anything else I can do to try and diagnose / troubleshoot?