I get an error message that says I need to update Java on my computer in order to upload an ibook to iTunes.
I heard that some downloads of the Lion version of the Java update do indeed have this problem. But running Disk Utility verify on the dmg shows its only because of a bad volume header in the dmg image and nothing really that serious (for a dmg). So you can continue with the mount with no fears.
I don't know anything about the "iTunes Producer" download so I cannot comment on it. Probably a similar problem.