Cable and satellite are LOADED with artifacts all the time. They cannot be used for ANY sort of evaluation. The compression applied to video (and audio) by cable and satellite services does not even preserve 1920x1080 resolution and, by all rights, the "HD" you get from cable and satellite should not be allowed to be called "HD". It certainly looks better than SD, but Blu-ray discs are the only true HD source we have right now. And Blu-ray is far from perfect... it really needs more bits (10 would help, 12 would be ideal) and less color decimation and a wider color gamut. In fact , during scenes with a lot of motion, I've estimated on-screen resolution from cable and satellite in the 200x100 range because the block artifacts are so huge. (just pause a frame on an explosion or some other full-screen motion using a cable or satellite DVR to see how horrible the resolution is).
That said, Toshiba TVs I've reviewed in the past have HORRIBLE problems generating posterization and block artifacts after adjusting the CMS controls more than 1/3 of their adjustment range (on TVs with adjustment ranges of +/- 10, I didn't see problems when using adjustments of +/-3 or less, with TVs having an adjustment range of +/-30, I was able to use adjustments up to +/-10 before seeing the artifacts. I didn't really try moving other controls much to see if that also produced artifacts, but it is possible they could. Toshiba designs seem to have limited capacity to make adjustments without negatively impacting image quality... at least for some controls.