I dont know if this is much help but, I noticed the same thing at the electronic store during a demo of HDTV. They were showing Discovery HD channel and it looked so good it almost seemed 3D. When he was asked to switch it a regular channel he turned on sci-fi channel. It appeared grainy to say the least. His explanation of this was that the HDTV had such high resolution that the TV was trying to fill in the gaps from the inferior analog signal channel. He said it created the grainy blurry picture. Of course he said said it wasnt a problem with the upcoming switch to hi-def signals but thats not untill 2006 if Im right. And even then stations may not broadcast in 1080i This is a cable signal and half of the channels are still analog.