Something I tried that helped a little was set the STB to 720p since that is what most broadcasts in HD use.
We have been having this problem since October. Everything has been switched out, tested, re-tested numerous times and it keeps getting worse each time. We have been told it is not an issue in our home, but the problem has not been resolved. The other night not only did we have a really bad pixilation problem the sound kept cutting in and out.