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
iTunes 10.5 Is Here –
Today is the start of a very busy week for Apple. To start it of the have made iTunes 10.5 Available to download the download button is not immediately visible from the iTunes home screen but click download and it will reveal the download button for iTunes 10.5. You can also get it from software update if you are using a mac
What’s new in iTunes 10.5
• iTunes in the Cloud. iTunes now stores your music and TV purchases in iCloud and makes them available on your devices anywhere, any time, at no additional cost.
• Automatic Downloads. Purchase music from any device or computer and automatically download a copy to your Mac and iOS devices.
• Download Previous Purchases. Download your past music, TV, app, and book purchases again, at no additional cost. Previous purchases may be unavailable if they are no longer on the iTunes Store.
• Sync with your iPhone, iPad, or iPod touch with iOS 5.
• Wi-Fi Syncing. Automatically sync your iPhone, iPad, or iPod touch with iTunes any time they’re both on the same Wi-Fi network.
For information on the security content of this update, please visit: support.apple.com/kb/HT1222