I'm not sure what this checkerboarding looks like, but I've got what can only be described as "checkerboarding" on this setup:
I thought it was an issue with the monitors being surplus and relatively well "used" and maybe developing some sort of problems with caps or whatnot. I would be very curious to see if this mod removes the pattern.
The CM7000 is a little pricey and harder to find than the usual suspects (Zenith, Insignia, DigitalStream, et. al.). Have you located this junction on other DTV boxes? Any plans to look?