This is a strange problem because there's no reason it should be happening.
I'm running xampp 1.7.4 locally and jquery-1.6-dev. I'm working through the "jQuery Novice to Ninja" book and everything is working fine until I hit Chapter 3 - animated navigation. Instead of displaying across the top of the page, the nav bar displays down the page. After double- and triple-checking everything I just straight copied the example files for the book into my local server. It did the same thing. In other words, when I double-clicked the file to view in the browser it worked, but the exact same file viewed in the server did not work. I checked with the file I was working on and sure enough the same thing happened - it worked viewed in the browser but not through the server. I hope I explained this clearly. Has anyone run into this sort of thing before? Is there something on the server that needs to be configured?