iTunes 4: "Shared Music Library Is Not Compatible" Alert

Computers with iTunes 4.0 are unable to share music with computers that have iTunes 4.0.1 or later installed.
Symptom

This alert appears: "The shared music library <shared library name> is not compatible with this version of iTunes."

This occurs when you click on a shared music library in the Source list.

Solution

If you are using iTunes 4.0
Download and install iTunes 4.0.1 or later. See the iTunes website for update information (http://www.apple.com/itunes/).

If you are using iTunes 4.0.1 or later
The computer sharing the music library to needs to update to iTunes 4.0.1 or later.

iTunes 4.0.1 only allows music sharing between computers using iTunes 4.0.1 or later on a local network (in the same subnet).
Published Date: Feb 18, 2012