With Lion, Xcode 4.1 is now free from the Mac App Store. While this is great, lots of people (myself included) have encountered a small problem during the installation.

Once the installer gets to the stage “Updating files…”, the following dialog appears:

In order to continue installation, please close the following application:
iTunes

No matter how many times you quit and re-open iTunes, the dialog refuses to disappear, and the installation is stuck.

It seems this must be a common problem, as Apple have posted a solution right at the top of the Xcode Developer Support Center. It turns out that the background process “iTunesHelper” is still running, and also needs to be quit. To do this:

1. Open Activity Monitor (located in Applications/Utilities)
2. Start typing “iTunes” into the filter box in the top right
3. Select iTunesHelper from the list and click the Quit Process button.

As soon as you do this, the dialog should close, and Xcode should continue to install.

If you are wondering what actually iTunesHelper does, it’s simply a small background process that watches out for when an iPhone, iPod or iPad is connected and automatically launches iTunes. When you install iTunes, it gets set as a login item, meaning it automatically starts up every time you log in. Unfortunately, after installing Xcode, I went to my login items (under Users and Groups in System Preferences) to find this:

It seems something (either the Xcode installation or the upgrade to the latest version of iTunes) had broken the login items link to iTunesHelper. Luckily this is easy to fix. Go find iTunes in the Applications folder, and right-click it and choose Show Package Contents. You’ll find iTunesHelper in the MacOS folder. Simply drag it across into your login items and everything should be back to normal.