First off, there's an interesting piece about whether or not velociraptors actually hunted in packs. Here's some of the original debate on the subject back in 2007:
Then from the piece from today...
Did Velociraptors Hunt in Packs?
While they discuss mostly the hunting behaviour of dromaeosaur theropod dinosaurs, they do mention the typical deinonychus as well, and to be honest, it's a wonder that dinosaur types like this don't get confused more often. I mean, just look at this piece from the Smithsonian site, that may may well explain the fact that it's likely Michael Crichton (who wrote the Jurassic Park books) may have confused the velociraptors and deinonychus.
But on such erroneous info are books and movies, some great and not-so-great, based, right? :)