this problem occurs on my tv as well as my brothers and my friends..
2 of us have a 505 and the other has a 505a (Starchoice HD in canada)
we all have different big screen HD tv's that are 1280x720

yet we all get a fair amount of macro blocking when watching live sports,,, in particular the NFL playoffs, but really only during closeups,, or where they show a closeup with a fast moving background,,, have also seen it on saturday afternoons when watching ncaa basketball on CBS HD,,,,

is this an issue with the receivers and the compression, is it a signal issue or can it be a TV issue,,,

LCD's are more prone to pixelation/macroblocking on fast moving shots. You don't say what type of TV you have. But all types of HDTVs get this problem sometimes. Whatever artifacts you are getting are generally the result of a compressed signal, more common with satellite, but it happens with any weak feed. So more info is really necessary, but if your whole family is getting it, it is the result of the quality of the HD signal you are getting.