There are some protected content CDs that do that. Name names.
This is the first time I've experienced this iTunes weirdness: last night, I attempted to import an audio CD into iTunes. The CD registered fine, with all the tracks showing up by title. But when I tried to play the CD, iTunes played only about a half a second of each song, scrolling through the entire CD. I then tried importing the CD without listening to it: iTunes said the import was successful, but only 1-3 seconds of each song was actually imported. I tried this with two different CDs, with the same result.
I'm using iTunes 4.9 on Windows XP.
Anybody have a guess?