Updates are sketchy business to begin with. Rarely do I do them. And here, we are all experiencing 'why'.
First, I updated iPod software and everything seemed fine (was still using iTunes 7.3) until I tried to listen to my pod. All the space was accounted for, but the songs, playlists, etc. all gone!
I read some other message board that suggested to simply download the newest iTunes 7.5. Problem is, I could never get it to load properly. I'd always get the same message that iTunes was, "missing files...Please re-load iTunes". Back to the forums & boards.
Finally, somewhere on one of these forums someone suggested this great fix which worked like a charm for me. First try and install 7.5.
Next remove Quicktime (usually the culprit) completely from your computer.
Then,Go to
http://www.apple.com/support/downloads/quicktime72forwindows.html
& download the Quicktime 7.2. Re-load & get going.
Voila! Finished. Hope this helps