If you attempt to install the Xcode 4.0.3, or Xcode 4.1 after installing iTunes 10.4, you may be presented with an installation alert asking to close the iTunes application.
To allow the installation to complete, use Activity Monitor to force the iTunesHelper process to quit:
- Open Activity Monitor (in the Utilities folder, which is in the Applications folder).
- Select iTunesHelper from the list of processes.
- Click Quit Process, in the upper left corner of the window.