JC,
Are you saying the best picture quality you have achieved is with s-video (not Component or DVI/HDMI) or are you saying your TVs highest resolution input is S-video (no Component or DVI/HDMI input on TV)?
Also, is the issue only with certain channels? All channels?
I had PC issues with TW and two things helped resolve the issue: 1. TW came in and checked the signnal strength. It was a bit low and they ran a new cable into the house and suggested a couple of changes to my in-house topology. 2. A new (different model) STB was much better than the previous model.
I currently have the SA Explorer8300HD which has the built-in DVR. It has exceptional PC over Component Video.
Enjoy,
TIC