Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
How to Set Up iCloud
You have probably heard of iCloud by now but just in case you are unfamiliar with it, it is a free backup service you can use for storage and syncing of multiple devices and it is of course for use with the Mac, iPhone, iPad and iPod so if you own any of these or plan to buy one, setting up iCloud is one of the first things you should do.
First things first, you need to sign up, but in order to do this you need to make sure you are using either iOS 5 or later, or Mac OS X 10.7.5 or later. Windows users can use iCloud but accounts must initially be created through an Apple device. The good news is, you are entitled to up to ten iCloud accounts per device but it is highly unlikely that you will need more than two or three.
You will need an Apple ID to create your account but if you do not have one, it is not hard to get one. Simply go to the iCloud settings screen and either tap on “Get a Free Apple ID” if you are using an iOS device or click on “Create an Apple ID” if you are using a Mac. Fill in the requested details and then choose between using an existing email address or creating a new iCloud-specific one. If you already have an Apple ID ready to use then it should already be entered when you get to the iCloud login screen. If you wish to convert it into an iCloud account, simply log in to the iCloud preference screen and it will guide you through.
Setting up iCloud on an iOS device is simple and the service can be accessed through Settings. From there, open iCloud and sign in, selecting “Get a Free Apple ID” beforehand if required. When your account is set up it should all start working automatically, syncing your email, contacts and much more. By default it syncs everything but you can go into Settings and be more selective by toggling the switches by each synced item. If you wish to create a backup, which is highly recommended, open Settings, select iCloud, then Storage and Backup and finally Back Up Now.
If you are using a Mac, go to System Preferences and open the iCloud settings pane. The setup procedure is the same as on iOS devices and once you log in with your Apple ID, it will guide you through the steps to set it up. The only option that is not automatically synced when you get started is Back to My Mac, which you will need to enable manually. As is the case with iOS devices, if there is any data you do not wish to sync, you can manually disable it. You cannot back up a Mac completely with iCloud but you can still store any data that is compatible with it.
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