I just switched from Cable over to Dish Network service. Now, I'm noticing black pixelation in certain areas when watching tv. It's especially noticeable when the tv is showing a closeup of someone's face. The pixelation tends to follow the contour lines on the face where there is transtion from light to dark color.
If it just appeared after the switch it may be due to signal compression used by the satellite company. They compress signals more than cable companies. Maybe they can boost their signal for you and it might help.