One good way to scrutinize the "dithering" problem is to push the freeze button located on the lower portion of the tv's remote.
I still am not convinced, though, that this is the TV's problem. If it were, the problem should be evident during similarly fast-motioned scenes on different channels, but this doesn't seem to be the case. I've only seen it on 2 channels.
Since owners' experiences with the Toshiba seem to differ so much, I am starting to think that performance is based mainly on feed, connections, and other equipment. For example, I get noticeable audio/video sync problems nearly half of the time, while others say they've never noticed it. I can't believe that some of the tvs are better than others.