Here's the official note from ABC's website. Looks like you were right, christmas87! To quote Charlie Brown: "Rats" (on it being aired Halloween night and not earlier.)
http://abc.go.com/shows/movies-and-...s-listing/its-the-great-pumpkin-charlie-brown
Thanks for the info! We have it on DVD, but it's still fun to watch it "live!" We have trick-or-treating that night from 6-8, so if the kids make it the whole time, we may have to DVR it and watch it when we get back.