I have many many albums and tracks purchased via the iTunes store both through iTunes directly and via the iPhone. They all synchronise properly and are on iTunes eventually (i.e. if purcashed originally on the iPhone).

There's one album, though, purchased via the iTunes app in June this year. Virtually every time I sync the iPhone it says "updating files" and this album gets updated. The rest of the sync goes just fine, new tracks added, listened to podcasts are removed, playlists are updated (notwithstanding that smart playlists' orderings are now utterly broken) fine - but this album is always getting updated.

In finder I've looked at the permissions and nothing seems unusual. FWIW, I'm on Mac OS X 10.5.8, iPhone 3.1.2, iTunes 9.02.

Anyone with any ideas?

It's not a fundamental problem, but it does means that each sync takes an extra 30-60 seconds, which is annoying!