I was just wondering what may be a few causes of a grainy image? I see grainy spots during Heroes, CSI, and a few other shows. Also, I assume it is normal to see a blocky background on SD channels. I'm watching on a Sony KDF50A10.
If you are talking about grain, it can sometimes be there as something the director desires to add "grit" to the programme. If that's not the case, then a proper setup of the TV can often lessen the "grain" - reducing sharpness, turning of edge enhancements, etc.