I've seen some of the episodes edited in their afternoon-slot (some of Kenny's dares in the episode where Cartman goes to fat-camp, for example). I think it's because those episodes are so much earlier than they normally are.
If you're talking about later airings than the afternoon-time, I dunno -- haven't noticed it yet.
--
http://img812.imageshack.us/img812/3492/eponaharr.jpg
Nominate E P O N A.