*bump*
I just noticed that I'm having the same problem. About a third of my iTunes library is not being transferred to my iPod.
I can't figure it out: all of the songs are checked off in iTunes and I've switched back and forth from manual to auto updating with no success. 2 CDs that I imported today didn't get transferred over. Very odd.
iPod software 2.1
iTunes 4.0
Powerbook 1GHz, 10.2.6
2.5 gigs worth of music missing on the iPod
Poking around the Apple KB, I haven't been able to find anything. I'm wondering if it has anything to do with my running an older version of iTunes (I dig the Internet-streaming feature, though I never use it).
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SOLUTION?!
I think I may have figured it out (as relates to my particular problem anyway). I found this article in the KB that describes the *opposite* of what was going on with me (just about).
http://docs.info.apple.com/article.html?artnum=42967
1.) I decided to restore my iPod to factory settings and reimport my entire library. It worked.
2.) After it was done, I went into the iPod prefs in iTunes and told it to auto update certain playlists only (I had recently done this for the first time a week ago when I decided that I didn't need all that bulk). I took out the smart playlists included in iTunes (My Top Rated, Recently Played and 25 Most Played).
It promptly erased half of the songs on the iPod.
3.) That KB article got me thinking that all of the songs that just got wiped probably occurred in those 3 playlists that I asked it to leave out.
After putting it back to updating all playlists, it copied everything back over and I'm good to go. Woot!
Hope this helps. I'm happy now.
