As for the first part of your question,I would make sure your TV is 1080P capable to get the PS3 to display 1080p on your TV. For the second question I have a Comcast motorola HD cable box and have not had the trouble you have mentioned although like BIG I use component cables to connect my cable box to my 970.
_________________________
Pre/Pro: 970
Amp: Rotel RB985
speakers: Paradigm Monitor3's all around
TV: Pioneer PDP5070HD